Brownie Science – Some chemistry & A recipe

One of my favorite sweets to bake must be brownies. Reason? They’re super simple to make and just about everybody likes them. Also, it’s easy to vary the recipe: what about walnut brownie, almond brownie or raspberry brownie? I’ve made them all, and they all taste good. But it’s not just flavour you can vary easily. By adjusting the recipe in a smart way, you can make more gooey, cakey or more chocolatey brownies. Once you understand the science of brownies you can easily adjust it to whatever you (or the one you’re making it for) like best.

Even though brownie science isn’t that complex (it’s a bit like waffle or pancake science), it has some more depth than you might expect.

Gooey vs Cakey Brownie

One of the most common brownie discussions on the world wide web is whether a brownie should be gooey or cakey. In other words, should it be moist, slightly sticky and soft or should it be fluffy, a little dry and crumble apart more easily?

Personally, I like brownies any way, maybe preferring them slightly gooey over cakey. But most important of all they should be fresh, a stale brownie is a real disappointment.

So what is the difference between the gooey and cakey brownie styles? The main difference between the two is the fat (= butter + chocolate) to flour ratio. More flour compared to fats will give a more cakey brownie. More fat on the other hand will make it more gooey. But oven bake time is also important, the longer a brownie is baked for, the higher the change of it becoming drier and more cakey.

In order to understand why the brownie behaves like that, we’ll take a deeper dive into brownie science! But before we do so, here’s a video from Martha Stewart, helping you understand the brownie consistency dilemma even better.

Brownie Science – The main ingredients

There a hundreds, no thousands of brownie recipes available. There’s gluten and milk free varieties (with avocado!), but here we’ll stick with a pretty basic brownie. The main ingredients of such a brownie are:

  • Chocolate: milk, dark or extra dark, for me a decent brownie contains chocolate, although you’ll also find recipes that only contain cocoa powder
  • Butter: the fat, this will contribute to the richness of a brownie, using margaring works fine as well, liquid oils can work, but the rest of the recipe will have to be adjusted since it will make the brownie a lot softer
  • Flour: keeps it all together
  • Sugar: it sweetens the brownie, but also contributes to the texture of a brownie, it can be white sugar, brown sugar, etc.
  • Egg: this keeps it all together as well, most brownies contain egg, if you leave it out, you will have to substitute it for another ingredient that binds and sets

With just these basic five ingredients you can make a brownie:

  1. Melt the btter & chocolate
  2. Mix in the flour, sugar and egg
  3. Bake in the oven

See, super simple. It’s nothing more than mixing and baking. The only reasons really for melting the butter and chocolate is to incorporate them evenly throughout the brownie. By melting the fats they mix very well with each other, but also with the other ingredients. Due to the high amounts of fat in brownie it also tends to be easy to mix in the flour. Flour tends to form lumps if there’s a lot of moisture (e.g. pancake or waffle batters), but with this high fat content that doesn’t happen. The fat will easily coat the flour particles.


Additional brownie ingredients

But that’s not all, even though you can make a brownie with these five ingredients, there’s so much more opportunity for variation. Let’s walk through these, before we dive into the details of recipe development for brownies.

  • Baking powder: Especially cakey brownies tend to be made with baking powder. Baking powder introduces air in the brownie, making it more airy and fluffy.
  • Salt: it’s in almost everything and can ramp up the flavour, but to be honest, you can often leave it out without any issues.
  • Cocoa powder: it can be used instead of chocolate, but you will often find it being used additionally, besides chocolate
  • Flavourings: vanilla extract is a common example of this one
  • Toppings: toppings don’t realy influence the brownie that much, you can add nuts, but also fruits to brownies without any issues. Found a brownie recipe without these toppings but want to use them? Just add them, it shouldn’t really give you any problems.

Brownie recipe develoment – Gooey vs Cakey

Now that we’ve listed the most important ingredients of a brownie, let’s zoom in on brownie science a bit more. We’ll focus on understanding the brownie recipe enough so you can start tweaking it to create your perfect brownie.

Role of butter & chocolate

Butter is 80% fat and chocolate tends to be at least 30-35% fat (depends on the type you buy though). The fats in both help create a rich, smooth brownie. A brownie without butter would become very dry and wouldn’t taste as rich. It’s especially this richness that you’re looking for in gooey brownies as well. However, don’t underestimate the importance of fats in cakey brownies. Making a cake without fat will give you a bread like consistency, thus a lot plainer.

Help, my batter thickens!

Making brownies starts by melting the chocolate and butter before adding the other ingredients. However, these will cool down again when the other ingredients are added. Upon cooling down they will firm up as well. Leaving a brownie batter on the counter for a while, will almost always result in a thicker batter. Nothing wrong here though, it’s just cooled down and the fats have set. Once you bake it, the fats will melt again.

Role of flour & sugar

The flour and sugar both largely contribute to the structure of brownie. Butter & chocolate itself will just melt into a puddle when placed into the oven, even if an egg is added. It’s the sugar and flour that thicken it and give it some sort of structure. Flour works by absorbing moisture in the batter, but once it’s being cooked the flour will swell up and thicken (remember making a roux?). The sugar doesn’t really transform during baking. Instead, sugar works by dissolving in the water in a brownie batter. By dissolving in the water, there will be less free water, thickening things up.

Both flour and sugar influence the consistency of the brownie. A lot of flour will result in a more cakey brownie. Less sugar will not only make the brownie less sweet, it will also make it less crispy (unddisolved sugar contributes to the crispiness) and softer as a whole.

Role of eggs

Last but not least the eggs. The eggs contribute greatly to gooeyness since eggs contribute moisture and fat. However, the eggs will also cook. This is due to the coaggulation of the proteins. These will form a network keeping everything together. However, if you overcook the brownie, these proteins will contribute to the brownie become drier by pushing out moisture instead of capturing it. Leaving the eggs out though will most likely result in a runny brownie that will never set completely.

3 Brownie recipes

All that brownie science made me experiment a bit with different ingredients and ratios of ingredients. So below you can find three different brownie recipes for three different brownie consistencies:

brownie experiment - three styles gooey cakey chocolatey
Three different brownie recipes: 1) the in-between variety, not too gooey, not too cakey; 2) the most gooey of the three; 3) for the chocolate lovers, most bitter, least sweet and slightly cakey due to the high cocoa powder content
  1. The basic recipe is a moderate brownie, it’s in between a cakey and a gooey brownie, slightly chewy.
  2. The second recipe is typically a gooey brownie, containing less flour to bind the brownie together.
  3. The last recipe is the most cakey brownie, it’s a little dry and very chocolatey, the least sweet, for the real chocolate lovers.

Cakey brownies
Prep time
Cook time
Total time
This recipe contains 3 variations of brownie. The first one is a basic recipe, not very gooey, not very cakey. The first one between brackets is very gooey, the second one is the most cakey and most chocolately, the least sweet also.
Serves: 25 brownie pieces
  • 160g (extra dark) chocolate
  • 195g butter (80g for recipe no. 3)
  • 240g sugar (180g for recie no. 3)
  • 150g flour (60g for recipe no. 2 & 3)
  • ¾ tsp baking powder
  • 3 eggs
  • (90g cocoa powder, for recipe no.3 only)
  • 1 tsp vanilla extract
  • ¼ tsp salt
  • Nuts (e.g. walnuts, almonds, pistachios)
  • Fruits (e.g. raspberries or blueberries)
  1. Melt the chocolate in the microwave (low wattage, max. 1 minute at a time and stir in between, if you don't have a microwave, use a the au-bain marie method, take an aluminium bowl or small pot and hang over a larger pot with boiling water).
  2. Add the butter and melt in the microwave as well.
  3. Mix in the sugar, flour and baking powder (as well as the optional extract & salt).
  4. Add the eggs, take care, the chocolate mixture shouldn't be hot (>50C) or it will cook the eggs.
  5. Either mix in the optional nuts now, or use them to decorate the top of the brownie.
  6. Pour into a pan lined with baking paper (approx. 15x15 cm), decorate the top with optional fruits or nuts.
  7. Bake in the oven at 180C for 30-45 minutes (time depends on size of baking pan, the longer you bake the drier it will become).

Good luck baking!


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