filled profiteroles with creme patissiere

The Science of Choux Pastry (In Profiteroles)

Choux pastry truly is a little piece of magic. It starts out as a small little ball of dough, but turns into a light, airy and fluffy hollow ball in the oven! It makes delicious profiteroles, éclairs, cream puffs and Bossche bollen (a speciality from the South of the Netherlands).

Recipes for choux pastry might look very complicated. You have to heat butter and water, mix it with flour and it somehow seems complicated. But, that’s mostly because it is such a different type of dough! Once you understand why you have to take those steps, it will become a lot easier to do and understand.

In this post we’ll zoom in on the science and reasoning behind a recipe. At the end you should know how to make a good choux pastry and understand what all the different steps are for (and which steps you can skip). And learn that it’s not at all that hard to make!

Already got your choux pastry under control? Then it’s time to make a filling, for example (our favorite), this creme patissiere or add a craquelin on top to finish it off!

What is choux pastry?

Choux pastry is the dough that makes profiteroles (see photo on top of this post), but also those beautiful éclairs. The main characteristic of choux pastry is that it forms a very airy structure with large holes that are ideal for introducing a filling into.

Choux pastry itself is savoury and doesn’t have a lot of flavour, it’s quite neutral, maybe a little eggy. That’s why the filling tends to be the element that makes a snack with choux pastry really stand out.

Making choux pastry

Choux pastry is its own type of dough. It’s probably most similar to hot water crust pastry since both doughs require you to cook the dough, before you put it into the oven. The dough is then baked in the oven which is when it puffs up.

Choux pastry is made of 4 ingredients, and each of these has a clear role in the recipe:

  • The water is required to make a flexible dough.
  • The butter serves to give the dough a richer feel and flavour. If no butter would be added, the choux would have more of a bread like consistency.
  • The flour gives structure to the final bun.
  • The reason eggs are added are various. First of all, it adds extra moisture to the mixture and makes it more flexible. It needs flexibility to expand. Second of all, the proteins will form a sturdy structure when heated, this will support the airy shape of the profiteroles. Third, eggs contain fat and prevent the puff from becoming dry.

What you’re trying to do while making the pastry, is to create a dough that is soft enough to expand, but firm enough to hold onto its shape before and after baking. To do so, you need to follow four steps:

  1. Heat up the water and butter
  2. Mix through the flour
  3. Add your eggs
  4. Bake the choux buns!
profiteroles with craquelin
Nice round choux buns with craquelin on top

Step 1: Boiling butter & water

You start by heating up the butter and water for various reasons. First of all, the butter has to melt, else we won’t be able to mix it through evenly, you might end up with lumps of butter. Also, the soft butter softens the overall dough consistency. When it cools down again, it will contribute to its firmness. Second of all, we need that heat to ‘cook’ the flour in the next step.

Most recipes call for bringing the water and butter to the boil. The reason for doing so is that it helps accelerate the next step. That said, you can still make perfectly fine choux pastry if you just heat the two enough for the butter to melt. You might need to stir a little longer in step 2 because you have to make up for that lost heat.

Step 2: Mixing flour with warm liquids

Once the butter and water are nice and warm, it’s time to add the flour. Just about all recipes say to add it all in at once and stir quickly. you should continue stirring until the flour + water & butter mixture form a nice ball. It shouldn’t puddle and that ball should still be soft and flexible.

During this step you accomplish an important step of choux pastry making: you cook the flour. The starch in the flour needs to gelatinize. When flour and hot water are mixed the starch granules within the flour will absorb water and ultimately swell and possibly explode. This releases starch molecules and is what thickens the mixture here. You need enough heat for this to happen.

This is very similar to what happens when using flour to thicken the filling in a pie or when making a roux for a bechamel sauce or for donuts.

choux pastry cooling down before adding the egg
Choux pastry after step 2, forms a ball which leaves the sides clean.

It is important not to stir the mixture for a lot longer than after it has formed the ball like consistency. If you continue stirring and heating the binding power of the starch can go down (kind of what happens to some more extreme in a dark roux). We did test heating and mixing it for a little longer than necessary. It did turn a little clumpy but the final profiteroles still turned out fine. Showing that there’s some flexiblity.

Why not merge step 1 and 2?

Technically, it is possible to add the butter, water and flour to a pan and heat and stir them all together from the beginning. For smaller quantities especially, your profiteroles can still come out perfectly fine. However, it is a lot more of a hassle. You need to be more careful not to get lumps or not to burn the mixture.

So why doesn’t the method really matter that much? Well, the main purpose of this treatment is to melt the butter, heat the flour, gelatinize the flour and form a thick paste. Whether you do that by heating on the fire or preheating liquid doesn’t really matter, as long as you mix everything homogeneously and don’t burn anything. The science stays the same!

Forgetting the butter or water

So what will happen if you forget either the butter or the water? In both cases, you’re up for a bit of a challenge, but there can be ways to fix it.

Forgetting the butter: This could give you a more chewy/firmer pastry. By whisking the flour and water without the butter, you run the risk of developing the gluten. Also, it’ll be hard to mix in the butter homogeneously in the little flour ball that will have formed. It’s probably best to start all over.

Forgetting the water: This shouldn’t give you as much trouble, the butter and flour will form a roux. As long as you remember in time that you’ve forgotten the water, you can still add it and thicken up the mixture.

Step 3: Adding the eggs

Now that you’ve got your ball of pastry, it’s time to take a break and leave it to cool down. You have to cool it down before adding the eggs, or you run the risk of cooking the eggs prematurely!

Eggs contain proteins. These proteins will curdle and set when the egg is heating. This is what happens when boiling or frying an egg. You want this curdling to happen once the eggs are in the oven since it will help stabilize the final profiterole. But you don’t want this to happen prematurely or they won’t be able to flex and stabilize the newly expanded structure anymore.

profiteroles + creme patissiere, ready to fill

 Step 4: Baking the profiteroles/choux pastry

Now that the eggs have been added, it’s time for the final step: baking the choux pastry. The choux pastry is placed on trays in either balls or longer slivers, depending on your final preferred shape.

During baking, the doughy, heavy pastry is converted into a light and airy puff, as is shown below. The dough is such that it is very flexible but also contains a lot of water. Because the flour has already firmed up during gelatinization it won’t break but expand because of all the evaporation of moisture inside the puff.

puff pastry behavior in oven
filled profiteroles with creme patissiere


Yield: 10 puffs/profiteroles
Prep Time: 25 minutes
Cook Time: 25 minutes
Total Time: 50 minutes

This recipe makes enough for 10 puffs. To amp up the flavour and texture, you an add a filling, such as a creme patissier. Of course, a lot more fillings would work, such as jams or just whipped cream.


Choux pastry

  • 50ml water
  • 25g butter
  • 30g flour
  • 1 eggs

Creme patissiere

  • 125ml milk
  • 1 egg yolks
  • 25g sugar
  • 12,5g flour


Choux pastry

  1. Add butter and water to a pan and heat it until it's boiling.
  2. Turn down the fire.
  3. Add all flour in one go and stir through, be quick here and keep on stirring until it has formed a ball.
  4. Turn off the heat and leave to cool.
  5. Once cooled to room temperature mix through the egg.
  6. Pre-heat the oven at 200C-210C.
  7. Place the mixture on a baking tray covered with baking paper. Make small piles of mixture, remember, they will puff up quite a bit so keep them small!
  8. Bake in the oven for 25minutes. They should start puffing up after about 10 minutes. Keep them in the oven until they are a nice golden brown and are dry on the inside.

Creme patissiere

  1. Heat the milk in a pan to just below the boiling point.
  2. Mix sugar and egg yolk. Once that's mixed, mix in the flour (do not mix in the flour from the start, it will make it a lot harder to mix without any clumps!).
  3. Slowly pour in a little of the warm milk and whisk through immediately (you have to make sure that the egg doesn't cook here, so mix quickly).
  4. Pour in the rest of the milk and whisk through.
  5. Pour the mixture back into the pan and heat while stirring. The mixture will thicken up, once it's thickened, take it off the fire and leave to cool.
  6. The creme patissiere will thicken further upon cooling so don't worry if it's not yet as thick as you would like. If it stays too thin try putting it back on the fire and heat through a little more.


If you want one of those perfectly round puffs, you can add a craquelin on top. It also gives your puffs just a little more oompf.

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  1. Hi! I am wondering what if you change the ratio of butter, eggs and flour. Some choux like ‘soesjes’ in the Netherlands are pretty soft while some other types have a crackly crust. Mind to share what could be the ingredients ratio change? Thanks!

    • Hi!
      Great question. I must admit, I haven’t tried this out myself (yet), but what I would advise is the following.
      The recipe in this post is probably more soft than it is very crispy. In order to make them more crispy, there’s two things you can do. One is to leave them in the oven a little longer. That way they dry out more and become more crispy. However, you will also run the risk of them becoming rubbery if they’re in too long.
      Another option is to tweak the recipe. If you do so, focus on varying the moisture content (the water) in the recipe. Adding more water will make it thinner. This will make it easier to expand and give it a thinner crust and make it more crispy. I’ve found recipes using almost double the moisture content as the recipe above, so there is some wiggle space, but you’ll have to experiment to find your optimum.
      That said, as with every recipe, and especially choux pastry, it is very dependent on the ingredients you use, especially your flour.

  2. Hi! Thanks for the great article! I was wondering if you could help me out with something, I have been making choux pastry for many years using electric ovens, now I have switched to gas ovens the choux doesn’t turn out as well, is there a different method to cook using a gas oven? Do i need to alter the recipe? Thanks for your help!

    • Hi Angela,
      Great question! Except for a short period of time a couple of years ago I have no extensive experience with a gas oven. That said, I was intrigued by your question, so did some searching around and think there are two reasons why your choux pastry isn’t coming out as nice (not sure what exactly is your problem, so I’m guessing that in the answer below):
      1. The moisture content of a gas oven tends to be quite a lot higher – This makes it a lot harder to brown your foods and makes it harder to dry them. As a result, they’ll stay whiter and because they don’t dry out as much it might be that they collapse again more easily.
      2. The heat in a gas oven tends to be more intense coming from the bottom. – This again makes it harder to brown the top, but this time because the bottom might have already browned enough and is finished before the top is. This can be reduced by placing the choux pastry up higher and I’ve read the advice to use a lighter coloured surface to bake them on.
      I wouldn’t expect you’d have to adjust the recipe. If you add less moisture they might crisp up faster, but then they’ll expand less well also. Adding more moisture will make it harder to them to expand properly.

      Hope it helps, good luck!

    • Hi Angela, I use a gas oven to bake my choux, I too was nervous at tgr start for the same reason, having being used to the electric oven.
      I use a lower heat and bake I haven’t timed it as such, but I leave it a bit longer… I preheat the oven at 160 deg…when the oven is ‘hot’ I put the tray in… but keep checking the rise and colour of the choux constantly… and they have always come out perfectly!

  3. Hello. This is a great article. Needed to understand the chemistry aka science.
    The article would be perfect if baking tips were added. I’ve seen lots of recipes with different baking temps and times. Some work and some flop. There are do’s and don’ts on the oven door opening. I had a bad experience with that while trying to manage a large batch! But you provided the part that was missing for me, and the tip for crisping the puffs was excellent.
    We’ll done to you and the replies from the community.

  4. hi,
    can you please advice something that can be used in place of eggs and also will replacing of the eggs cause any weakness to the pastry.

    • Hi Simran,

      That’s a great question, but a complicated one! You definitely can’t just remove the eggs from choux pastry. The eggs cooks in the oven and give the final choux structure and help prevent it to collapse. I haven’t tried any alternative to egg, if I were you I would buy one of the many egg replacers you can buy online. These are often a mix of starches which should help give some structure. Follow the instructions for your specific replacer and keep in mind that egg is for a large part moisture so you will have to make up for any loss of that moisture. The dough needs to be liquid enough to that it remains flexible and expands well in the oven!

      If you give it a try, let me know how it went!

  5. Thank you for a more technical based article. I prefer understanding the chemistry of the ingredients and the mechanical (technique) reasons for why a recipe works. It allows you to understand what steps you can be a little loose with, which ones are critical, and what you can substitute from a base ratio of ingredients. Here are some questions I hope you can find the time to address:

    1. Isn’t the only goal of ‘cooking’ the panade starch gelatinization? If so, then with a given volume of water and butter barely brought to a boil, adding a given amount of flour immediately reduces the temperature to a certain range. Isn’t the goal then to bring it up to ~135-140 F (the gelatinization of wheat starch) and hold it at that temp to achieve gelatinization, while avoiding evaporation as much as possible to retain the correct ratio of water in the panade? How long you need to hold the temp at ~135 F I’m not sure, but I would guess not very long, 1-2 minutes? Egg white proteins set at ~144 F, so as long as the panade’s temp is less than that, we can add the eggs.

    2. So many choux recipes warn about slowly adding the beaten egg to achieve a correct batter consistency, but if your recipe is scaled to say 4 Large eggs, and if my assumptions in #1 are correct, and we’ve avoided too much evaporation, then shouldn’t we be able to just dump in four eggs and not worry about the consistency of the batter as you do here? Large eggs vary in weight by only ~2 g / egg. So with 4 eggs, we can only be off by ~2 tsp. (4 eggs @ 2 g ea = +/- 8 g, or about 12% of one large egg).

    3. Wouldn’t one explanation of cracked buns be a lack gelatinization? Isn’t it the gelatinized starch that helps the batter to stretch and expand without cracking?

    Thank you for your time

    • Hi Darrin,

      Great questions! I’ll do my best to answer them:

        Yes, I agree, starch gelatinization is the major thing you’re trying to here. You theory to me sounds correct, but with a few comments. If you heat the panade to higher temperatures than the starch gelatinization temperature, the gelatinization will go faster. Therefore, you could theoretically hold it at the exact right temperature, but you might need a lot more time (a bit like boiling an egg in boiling water vs. at the exact right temperature for the egg white to set). As long as you don’t literally boil your mixture, I wouldn’t expect you’d lose a lot of moisture during this step indeed (unless you boil your water for a long time before adding the flour).
        Also, yes, you can add the eggs as long as the temperature is below that of setting the eggs. You could add them even when it’s a little warmer since the egg will cool down the mixture, but in that case you have to mix well while adding it to avoid any scrambling. I wouldn’t expect that you’d need to vary the amount of eggs. The only thing I’d be worried about possibly is adding too much liquid too quick which may make it harder to break down the batter. If the mixture is very liquid, lumps tend to be harder to get rid off. That said, that still wouldn’t require a slow pour, you could avoid that problem by adding the eggs in two portions (bit like you would do for making batters, although for batters it is more crucial since there’s not as much fat in there).
        Hmm, I’m not too sure about the answer on this one. Both the starch as well as the eggs play a role here is my assumption. The gelatinized starch is what gives the pastry the stretchy nature that will allow it to expand. Important there is also that you’ve got enough moisture in there at the start to keep the batter flexible. If it’s too dry it won’t be flexible either. The starch itself won’t necessarily cook as much since the starch was already gelatinized. Instead, I’m expecting the cooking of the egg (proteins) to be important for setting the choux bun in place.

      Hope that gives some helpful additional thoughts! Let me know if you’d like to discuss further, these are great ideas!

  6. hi thank you for a great article on choux. i have a question regarding my choux pastry. i tried to make them everything was fine but one thing that i notice is that the middle of the puff was not dry. i bake it at 190 degree celsius at about 28 minutes it was already very golden brown. what do you think went wrong? and can u give me tips to make the puff very hollow in the middle? thank you

    • Hi Vania,

      Thank you for visiting! It sounds like you have an issue of the outside baking too quickly for the inside to properly cook. This can best be caused by two things:

      1. The oven temperature is too high, cooking the outside quickly while the heat does not have enough time to travel to the inside of the choux. This can be solved by reducing the temperature of the oven next time you’re baking your choux. Try 20C lower to start with. This way, your choux should have more time to dry out.Unfortunately, every oven is different so you may have to adjust your oven settings for this one. Gas vs electric and conventional vs. convection all give different results.
      2. The size of your choux buns is bigger than given in the recipe. Larger choux buns need more time to fully cook than smaller choux buns do. Reducing the size of your choux buns would likely help as well.

      And to make really big puffy choux pastry you will have to fully optimize your recipe which will mean a little trial and error. You get the biggest choux pastry bun if your batter is just the right thickness. Too thin and it will run all over your trays. Too thick and it won’t puff as easily. Whereas this recipe gives good choux buns, the exact structure will depend on exactly how big that egg is and thus how much moisture you add. Try a few different ratios, slightly increasing or decreasing the amount of egg and see what happens and what works best for what you want to achieve!

      • Hi thank you for your advice
        tried lowering down the temperature and its working! and i adjusted the recipe where i added more water and decrease the amount of egg. still not a 100% what i wanted but its getting closer. still need to do some trial and error. but i have another issue, im using craquelin on top of the choux but i realize that then the choux is cooled and a slight touch made the craquelin fall apart from the shell. is this normal?

        • Hi Vania,

          Great to hear it’s working better now! I had never made craquelin before, so made sure to try it before answering your question. That some of the craquelin falls off isn’t uncommon, however, it shouldn’t all fall off! An option is to reduce the thickness of the craquelin, making it a little more sturdy.
          Also, we just published a separate post on craquelin, hope that will help you in your quest for the perfect choux + craquelin!

    • Hi Nicole,

      Thanks for stopping by. I have not tested corn starch instead of flour and would expect it to behave quite differently. Corn starch probably won’t be able to give you the ‘stretch’ you’re looking for when the choux buns rise.
      You can give it a trial and then I would start out with slightly less (probably 75%) so you can adjust based on the consistency of the dough in the pan.

      Good luck!

        • Hi Nicole,

          Sorry about that! Replacing flour for corn starch in the pastry cream will definitely have a migger chance of success! Since corn starch is almost completely made up of starch, whereas wheat flour still contains some other components I would start by adding 3/4 of the weight of the flour in corn starch. If it doesn’t thicken enough, you can add more later (but always make sure that you mix the corn starch with a little cold moisture first before adding it to the hot mixture or it will clump!).

    • Hi Jamey,

      Thanks for coming by and glad to hear you enjoy it! I write under the pseudonym Julie Mal.

  7. Hiii,
    This article is amazing. I’m wondering when you would add flavour to your choux pastry? Before the eggs? During? Does it differ if the flavouring is a liquid, paste or powder?


    • Hi Harmeet,

      Great question!
      I would personally add flavor to the filling of the choux pastry, as opposed to the choux itself. Also, you could consider adding a craquelin. Reason for doing so is that first of all the filling makes up more of the final choux and so can be a real flavor bomb. Also, the filling tends to be way less delicate and flexible, making it easier to add fruit purees, etc. You just have some extra flexiblity.

      That said, you can add some flavor to the choux pastry but you have to be careful not to impact the texture of the choux too much (I haven’t tried it myself). Generally, flavors are very strong, so you need only very little so it shouldn’t impact your texture too much, but do keep an eye on it. If your flavor is liquid, you might need to add a little less liquid from your recipe and vice versa if you’re adding some powders.

      Keep in mind that a lot of flavors evaporate easily and might evaporate in the oven when baking your choux pastry so you might not get as strong a flavor as you were hoping for.

      With regards to when to add the flavor. Assuming it’s a strong flavor, so with only a small quantity, I would add it right at the end, after you’ve added all other ingredients. A quick mix in should do the job.

      Also, while writing this I was thinking of another option (haven’t tried it myself, but might be interesting). You could also try to infuse the butter + water with a flavor of your choice using spices. E.g. take cinnamon sticks or anise seeds and let them sit in warm butter + water for a while, it might just add a subtle hint to the batter (read more here).

      Hope that helps! Would love to hear what you find when you try it out :-).

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