Cinnamon french toast with icing sugar and grapes

The Science of French Toast – Choosing the Best Ingredients

One of the first foods I learned to cook is French toast. Don’t ask me why, but our school’s cooking classes started by teaching us how to make French toast. Of course, over the next several weekends, I wanted to make French toast over and over again, proud of the new skills I learned, but also just enjoying the French toast!

French toast isn’t just a relatively simple recipe to make (as long as you choose your bread wisely, more on that later), it’s also a great way to use up left-overs. And, since you only use a few ingredients, it’s perfectly suited for extensive experimentation!

What is French toast?

Drilled down to its core, French toast is bread that is soaked in liquid (nowadays often milk and egg) before being fried off in a frying pan. It’s not a recent invention, at all. Instead, some version of it may date as far back as the Romans did.

French toast isn’t unique to the French either (nor is it specifically French). As a matter of fact, a lot of countries all have their version and accompanying names: such as the Poor Knights (of Windsor) in the UK or pain perdu (lost bread) in France. In Dutch, they’re called wentelteefjes, likely referring to the fact they need to be turned over frequently.

Reason for this ubiquity and long history is its usefulness. French toast, or any of its variants, is perfect to use up old, stale bread and make it into something delicious again.

What is the best bread for French Toast

The use of stale bread requires us to take a closer look at the bread used for French toast. Whereas historically it’s likely been developed to use up old stale bread, nowadays, most recipes use fresh bread. Both work, of course, but there’s a lot of choices to make when choosing your bread for French toast.

When choosing your bread, keep in mind its function in French toast. It it what forms the overall structure of your French toast. Of course, bread also adds flavor, some more than others. Last but not least, bread contains sugars and proteins. These will react with the batter when it’s being fried, creating various delicious aromas and flavors.

Fresh vs Stale vs Dry

Freshly baked, still warm, moist bread, even though it’s delicious, is not necessarily your best choice for French toast. This bread isn’t as good in absorbing and holding onto liquid. It’s best if your bread isn’t fresh out of the oven.

Then there’s stale bread. Stale bread is slightly drier as a whole then fresh bread, though not necessarily by much. More importantly, it’s become more crumbly and chewy due to the restructuring (retrogradation) of starch over time. Stale bread is better at absorbing moisture, but the main benefit really is that the extra moisture and heat revive the stale bread, greatly improving its quality.

Lastly, there’s the dry bread, for these seeking French toast perfection. According to several tests online, your bread can absorb even more liquids if you dry the bread in the oven first. The extra liquid within can make it even more creamy.

If you’re talking just how much of an upgrade French toast is to your slice of bread, stale easily wins from fresh bread. Up to you whether that’s actually important!

No big holes in your bread

French toast is all about bread absorbing liquids before frying it. In order for bread to soak up any of these liquids it needs to have a close knit structure that can absorb the moisture. If your bread has a lot of very big holes, that’s not going to help it absorbing that moisture. The layers of actual bread might become too thin for it to hold onto a considerable amount, both during soaking & subsequent frying.

Some holes aren’t an issue though, but if you’re into optimizing your French toast, limit those holes.

seeded sourdough bread slices
This bread has a few large holes, but should still make a perfectly fine French toast, don’t go for much bigger/more holes!

Slice thickness

The two main factors that go into deciding your optimal slice thickness are: your own personal preference & ease of frying.


Let’s look at the latter first. When you soak bread in liquid it can become very soggy and fragile, especially if you don’t just dip the bread but soak it in for a while. Part of the bread literally starts to dissolve in the liquid and the overall structure weakens considerably. Bread is a foam, that holds its shape thanks to the starchy structure within. Once this starch absorbs moisture, it loses it’s strength. (Note, if you’re using stale or dried bread, your bread can handle a lot more moisture before becoming too soggy.)

A sturdy crust can help to keep it all together, as can a quick dip instead of soak in the batter. But, you can also decide to use a thicker slice. For a thicker slice, it takes longer for the whole slice to soak through. Also, a thicker slice has an easier time holding onto its structure. A thinner structure is simply not as good in holding onto itself.

Personal preference

When it comes to personal preference there are a few things to consider. First of all, how the French toast is cooked. When you’re cooking French toast you’re creating two different layers: one, a crispy outside layer, second, a soft custardy center. The thicker the slice, the more of that custardy center you will get. If you prefer the crispier outside layer over the center, you’d probably want to go for a thin slice, and the other way around if you prefer the center.

Second to consider is your ratio of toppings to French toast. If you like to dust your French toast with powdered sugar for instance, you’ll need considerably more on a thick slice than on a thin one to get the same ratio of sugar to toast!

making french toast, the batter and bread
Making French toast with thin slices, my personal preference!

Type of bread

Last but not least: there’s the type of bread you’re going to use: white, whole wheat, with seeds or nuts, or just plain. Almost all of them work and again, it’s mostly about what you’re after in your French toast.

Do you want a rich, almost creamy delicacy? In that case, an enriched bread that is made with butter and/or eggs would be a good choice (e.g. a challah or brioche).

Are you looking for some extra crunchy and texture in your French toast? Try using a bread with some nuts throughout or some seeds. Remember that French toast doesn’t have to be sweet! It can be savory as well.

Do you want more flavor than just sugar and eggs, than a whole wheat bread, with a stronger flavor than its white counterpart would be a good option.

And of course, if you just want to use whatever bread it is you have left, that will likely work as well!

The best ‘batter’ to dip your French toast in.

Now that you’ve chosen your bread, it’s time to choose a batter to dip your bread into before frying it off! This is where a whole next level of experimentation can set in. Let’s look at what we need in the batter.

First of all, we need that liquid. The liquid will help soften the bread and create that richer texture. Next, we need something to help set that liquid. If you’d just dunk bread in water and fried it, you wouldn’t create that nice crunchy layer, likely, you’ll just end up with soggy bread. Last but not least, we can add some extra flavor by adding some spices, sweetness, extra brown color.

The liquid (e.g. milk)

The simplest liquid you can use is water, as long as you add something to bind it during cooking. However, water doesn’t add much else, no flavor and no texture either.

Most French toast therefore uses dairy milk. Milk adds the moisture, but it also adds some fat (unless you use skimmed milk) as well as some sugar (lactose) and proteins. The sugar and proteins will react when heated in the pan, in a reaction called the Maillard reaction. Upon reacting they create a lot of delicious flavors and aromas. The proteins can also contribute a little to texture, but the role is quite minor.

Technically, you can make French toast with other types of ‘milk’ as well. Nut milks and oat milk for instance both add both moisture, as well as fats, proteins, some sugars and flavor. They’ll all give a slightly different flavor, but can all serve their purpose in French toast.

The binder (e.g. eggs)

Next up, the ingredient that binds it all together and firms the liquid up upon heating. Most French toast recipes will use eggs to do this. Eggs are great at it. The proteins in eggs solidify upon heating, firming up the liquids in the bread. What’s more, egg adds fats for richness and they are don’t ‘hide’ flavors. Make sure to whisk the egg very well before adding it with the other liquids or you’ll see pieces of cooked egg on the outside of your French toast that haven’t been absorbed well.

Instead of eggs, you can use other ‘binders’ as well. A commonly used method is to use corn starch. You can easily whisk corn starch through your liquid (though start by adding only a little liquid so it doesn’t clump up). Corn starch absorbs and holds onto liquid when it’s heated, making it great for binding liquid (as we do when making eggless ice cream or cake as well!). The disadvantage of corn starch can be that it also ‘hides’ flavors, so don’t overdo it.

The extra’s

This is where you can go all out! The extra’s don’t contribute as much to the core structure of your French toast, so you can experiment more freely.

You can add extra sugar to the liquid. The extra sugar will caramelize and participate in the Maillard reaction, contributing not just sweetness but a lot more flavors. You can add any type of sugar, granulated, icing, brown sugar or panela.

Next up are the spices. Cinnamon is a very popular combination with French toast (my personal favorite for a sweet version). Vanilla is a close second, although personally, it’s not my favorite. Nutmeg, maybe even some chili for a hit of spice or allspice and cloves are great as part of the spice blend to remind a lot of us of the autumn season.

Cinnamon french toast with icing sugar and grapes

Experimenting with French toast

Now that you’ve chosen your ingredients you can experiment and optimize your French toast. Everyone prefers theirs a little different, there isn’t such a thing a one perfect French toast!

So, let’s see how you can optimize and tweak yours, apart from all those variations in ingredients you can choose from. Keep in mind that you’re not just limited in which ingredients you use, you can also change your method of cooking. Here we’re limiting ourselves to pan-frying, but you can also bake your French toast in the oven!

Firmer texture:

  • add more binder
  • soak for a shorter amount of time
  • add less liquid

Soggier/softer texture:

  • add less binder; don’t reduce it too much or it won’t set anymore
  • add more liquid
  • soak for a longer period of time

Browner color:

  • add more sugar to get more browning reactions going on
  • use a liquid with proteins and or sugars to help browning reactions

More crispy outside:

  • adding more sugar can help here by forming a caramel-like crust
  • add less liquid
  • bake at a higher temperature
french toast with ketchup

Time to enjoy: the toppings

Once your French toast is ready, it’s time to enjoy! You can eat it as such, or at something on top. Personally, I enjoy my french toast with icing sugar, sugar syrup or some sort of chocolate topping (sprinkels or spread). Adding some fruits makes it even better.

But tastes differ, someone I know happens to prefer to eat theirs with ketchup! Nothing else.

What about you?

Cinnamon french toast with icing sugar and grapes

Basic French Toast

Yield: 6 slices
Prep Time: 5 minutes
Cook Time: 15 minutes
Total Time: 20 minutes

A basic French toast recipe, a good starting point for further experimentation to make your favorite version.


  • 1 egg
  • 200 ml milk (if you like it eggier, leave out some of the milk and keep back a slice of bread)
  • 1/4 tsp cinnamon
  • 1 tsp sugar
  • 6 slices of bread (approx. 0,5cm thick)


  1. Mix the eggs and the milk in a bowl until the eggs have been mixed through well.
  2. Add the cinnamon and sugar and whisk through quickly.
  3. Take the slices of bread and soak them in the mixture one by one. If you're using thin slices this should only take a few seconds. If you're using thicker ones you might want to leave them in for a little longer and you won't be able to soak as many of them since they each soak up more.
  4. Stack the slices on top of one another until you're ready to fry. This way, the moisture will soak from one into the other. If the bottom one becomes too soggy, just turn the pile over!
  5. Heat a little butter in a frying pan.
  6. Once the pan is hot, turn it to a medium heat and add soaked slices of bread. Add as many to the pan as fit comfortably next to one another.
  7. Turn the slices once the bottom has browned slightly. It should come off quite easily. Flip and bake until both slices are a nice medium brown. If your French toast keeps on burning before being cooked through, lower the heat down.


If you'd prefer to make French toast in the oven, we've got a recipe for that as well!


Dassana Amit, French toast (eggless French toast), Dassana’s Veg recipes, Aug, 16, 2019, link

Cook’s Illustrated, French Toast, Jan/Feb 2009, link ; this recipe (behind a pay wall) dries the bread before making it into French Toast

Food Timeline, French Toast, link

What's your challenge?

Struggling with your food product or production process? Not sure where to start and what to do? Or are you struggling to find and maintain the right expertise and knowledge in your food business?

That's where I might be able to help. Fill out a quick form to request a 30 minute discovery call so we can discuss your challenges. By the end, you'll know if, and how I might be able to help.

headshot Annelie


  1. Skip the milk and do not soak. A few seconds is enough. It won’t end up like an omelette as mentioned above, and you will end up with a nice firm french toast without the dreaded soggy/custardy center. Soggy french toast is always a sign of over-soaking.

    • Hi, Thanks for that addition. It makes a lot of sense not to soak for too long indeed, especially with thick slices where cooking that center is so challenging!

  2. I use heavy cream instead of milk. The rich density gives it not only flavor but a nicer texture when its cooked thoroughly. The bread seems to rise a bit. I also use vanilla extract as my sweetener. Just a little drop or two for 2 eggs and 3-4oz heavy cream. If I really am craving sweet I crush up Graham crackers and after dipping the bread in the egg mixture I the coat it with a dusting of the Graham crackers and oh my goodness are they yummy with some yogurt and strawberries!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Skip to Recipe