choux pastry puffs, freshly baked

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 little hollow ball in the oven! It makes delicious profiteroles, éclairs, cream puffs and Bossche bollen (a speciality from the South of the Netherlands). There’s a few little tips and tricks to make sure the choux pastry does turn out light and fluffy.

Recipes for choux pastry might look very complicated, however, 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!

What is choux pastry?

Not really sure what choux pastry is? 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 can be filled with any filling. Choux pastry itself is savoury and doesn’t have a lot of flavour, it’s quite neutral, therefore the filling tends to be the element that makes a snack with choux pastry really stand out.

Making choux pastry

Pastry choux recipe
Choux pastry recipe visualization, makes enough for 150g dough.

Choux pastry is a dough that has to be cooked, before baking in the oven. This makes it slightly different from most others. The process above describes the cooking section. Once you have this dough, dose it in smaller balls and bake in the oven (220°C, duration strongly depends on the size).

Now that we know how it’s done, let’s zoom in on why it’s done that way.

Step 1: Boiling butter & water

Choux pastry is made of only a few 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.

Why heat the butter and water?

There are two reasons here. First of all, the butter has to melt, else we won’t get a soft and flexible dough and won’t be able to mix it in. Second, we need the two ingredients to be warm to make sure the strach in the flour of the next step will gelatinize.

Gelatinization? Flour contains starch and when starch is mixed in hot water, it will absorb water and start swelling. This will give a nice thick gluey consistency. 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.

A question does rise up. Why boil the water and butter and not just heat it?

Step 2: Mixing flour with warm liquids

It’s time to add the flour now. Just about all recipes say to add all in at once and stir quickly. It should be stirred until the dough forms a ball. This will give the right consistency to continue and shows that enough water has been absorbed and starch gelatinized.

But why can’t we merge these two steps into one (so just heat water + butter + flour and mix while heating)?

The Experiment

In order to see whether the two steps can indeed be merged, I performed a little experiment. I made a total of four different batches in which I changed steps 1 and 2. However, the last few steps, mixing in the egg and baking in the oven at 220°C for 10-12 minutes were done in the same way. Here’s what those batches looked like.

Batch 1 Batch 2 Batch 3 Batch 4
  • Bring water & butter to a boil
  • Add all the flour, mix
  • Heat until it forms a ball
  • Do as mentioned in two, but: keep on the heat for several extra minutes after it has formed a ball
  • Heat water and butter until all butter is melted, but do not let it boil (<60°C)
  • Add all the flour and mix.
  • Keep on the heat and mix until the mixture forms a ball
  • Put all flour, butter and water in a pan.
  • Heat on the fire while whisking until the mixture forms a ball.

The Results

First of all: all 4 methods gave puffy profiteroles! All four methods worked fine without any big issues. We, non-profiteroles/choux pastry experts couldn’t taste a difference. Only difference was that those of recipe 2 might have puffed a little less, but still, they puffed.

So what happened? Let’s start with recipe 3. After adding in the flour with the melted butter and water, the mixture looked very liquid, see photo below. However, I just kept stirring and heating the mixture, and voila! It turned into a ball as well (photo on the left). This is exactly what happens when making a roux.

Recipe 3, after it’s been heated and stirred for a little longer Recipe 3, just after the flour has been added to the butter & water
2015-10-03 14.33.35 2015-10-06 20.26.25
Recipe 2, after it had been heated in the pan too long. The inside of a nice little puff

The exact same happened for recipe 4. It needed some careful stirring, but in the end it also turned out fine. The main risk with method 4, especially if you’re making larger batches, is that it will be harder to mix everything into a homogeneous mass without anything burning before all butter has melted. Apart from that, it works just fine.

Continued heating of the ball after the ball has been formed doesn’t make it look very appealing (see photo, you can see clumps, it seems to have separated). However, it also turned out just fine at the end!

I prefer method 4 since it just saves time and fuss. But, when making large quantities (think more than a kg or so), I would prefer method 1 (the original one) since it’ll be harder to whisk that through.

So why doesn’t the method really matter that much? Well, as I explained above, 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!

More variations

There are of course a lot of other changes we could test. We won’t do that here, except for one. What if you notice that you forgot to add either water or butter to your mixture after adding the flour?

Forgetting the butter: My hypothesis is that 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. My advice: start over. Note that with the other recipes (e.g. scones & pies), butter can prevent extensive gluten formation.

Forgetting the water: This shouldn’t give you as much trouble. It’ll be a little like making a rough. Just remember fast enough that you’ve forgotten the water, else your roux will turn brown, you’r making a dark roux and this will be very flavourful, but doesn’t have as much thickening power.

Step 3: Adding the eggs

Ok, we’ve finally made our ball of nearly-finished choux pastry. Now it’s time to take a break and leave it to cool down. Unfortunately, no short cuts here, do not skip cooling! Why?

Eggs contain proteins (learn more here). 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 (more about that later), not before. By cooling down the mixture before adding the eggs curdling of the eggs is prevented.

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. This is the curdling and denaturation I was just talking about when discussing the moment at which to add the eggs. Third, eggs contain fat and prevent the puff from becoming dry.

filled profiteroles with creme patissiere Step 4: Baking the profiteroles/choux pastry

Now that the eggs have been added, it’s time for the final step: baking the pastry. Make little balls of the dough and place these on a baking tray. The choux pastry should be baked at 220°C, probably 10-12 minutes (if you’re making small profiteroles, else it will be longer).

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.

choux pastry science
Baking puff pastry, water evaporation causes the puff to puff.

That’s it, now your all set to make some delicious profiteroles. While they’re baking, be sure to check out how to make creme patissiere. The puffs themselves are pretty bland in flavour (they don’t have any sugar) and this creamy filling will make it into a perfect little snack.

Profiteroles – the recipe

Since you can’t really eat choux pastry by itself, the recipe below also contains a suggestion for a filling: creme patissiere. Of course, feel free to ad other fillings such as whipped cream or jams.

Yield: 10 puffs/profiteroles



My profiteroles, written down in a concise matter! This recipe makes enough for 10 puffs with a creme patissiere filling. Of course, you can also use a different filling (e.g. whipping 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 of 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.




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  • 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.

  • 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!

  • 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.

  • 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!

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