Genoise cake – A baking guide by unravelling its science

Back in the days, before they had access to baking powder and baking soda, bakers had to be a bit more creative in how they were going to create light airy cakes and sponges. They couldn’t use the chemical reactions that make gas in a baking powder. Besides using yeast, another way to add air into a cake is by whipping it in even before the cake is in the oven. For that to work though, you’ll need something that will hold on to that air between the time it’s introduced and when the cake is fully baked and strong enough to hold on to it itself.

That’s why bakers used eggs. Eggs are very good in holding on to air, it’s why they’re the basis for a meringue. In a Genoise they also serve a crucial role. About time to take a closer look at this cake type.

What is a Genoise?

Or Genoese or Genovese? These are all names for the same cake which is based upon whipped eggs with sugar and with folded in flour and butter. A Genoise contains only little fat has quite a light delicate texture.

The name sounds as if it originated from Genoa, which is in Italy, but it’s a staple of French baking techniques. A Genoise is an interesting cake because of all the steps involved in making, it’s not as easy as this cherry cake, where you can just mix together all ingredients. No, there’s an order of doing things.

A recipe for a Genoise

Before walking you through the why’s of the different steps to making a Genoise, it will help you to have a recipe to refer back to. If you’re running into issues, have a look at our troubleshooting guide at the end of this post, together with the science explanations that should help you make a great Genoise!

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Genoise cake with jam, nutella and cream

Genoise cake

  • Author: Science Chef
  • Prep Time: 25 mins
  • Cook Time: 25 mins
  • Total Time: 50 mins
  • Yield: 12 portions

Ingredients

  • 4 eggs
  • 125g sugar
  • 100g flour (regular or cake)
  • 100g melted butter

Optional

  • For a bit of flavour, add the zest of 2 limes or a large orange

Instructions

  1. Whisk the eggs until they’re light and fluffy. Add the sugar and whisk it through.
  2. Take the bowl of mixture and place it above a pot of boiling water. Continue whisking until the mixture has warmed up slightly, then continue mixing away from the water until you’ve reached a ribbon like consistency. The mixture will still flow and form ribbons on itself (see text for a more detailed evaluation of this step and whether or not you really have to heat).
  3. Carefully fold in the flour to the egg mixture.
  4. Drizzle the butter into the mixture and fold it in as well, take care not to mix it too vigorously.
  5. Pour into a 24cm pan (if you want to create a large, but only a few cm high cake) which is lined with parchment paper on the bottom.
  6. Bake in a pre-heated oven at 180C for about 25 minutes until it is a light golden brown.

Whipping up whole eggs instead of egg whites

When making meringues, an Angel Food cake or some Eggnog you whip up egg whites, without the yolk. In those cases you’ll be told to definitely not add any egg yolk or it will break down the foam. However, for a Genoise you do add the egg yolk, why is that.

First of all, the foam you’ll be making for the Genoise will never be as firm and stiff as one you make for a meringue. An egg white can be whipped up so strongly that it will stay in its bowl, even when you put it upside down. However, these whipped eggs with sugar will never get to that stage. That doesn’t mean though that you cannot incorporate any air, it will just be less.

There are a few advantages of also adding egg yolks to the mixture. First of all, they create a richer cake since they add some fat to the cake. Overall this will create a richer, but more yellow cake. If you find a very white cake, it probably won’t contain the yolk.

Since the mixture is not as firm it can still rise in the oven. The heat will cause the air bubbles to expand. Since the mixture has not been fully saturated with air yet, it can still hold on to extra air. For cakes risen with egg whites only this tends to be a lot less. If you’ve made meringue before you will notice that most meringues barely, if at all, rise in the oven. They’re already as full with air as they can possibly hold on to!

genoise cake with caramel cream and walnuts and chocolate chips
A thin Genoise cake topped with whipped cream (flavoured with caramel) and walnuts pieces and chocolate chips, great combination.

Heating up whipped eggs

Many Genoise recipes call for heating the eggs and sugar either during the whole period of whipping, or for part of it. The reason for heating is that it will help denature the egg proteins which will again help it hold on to more air. Also, at higher temperatures sugar dissolves more easily into the eggs. However, you cannot really heat the mixture too much or it will cook the eggs.

Whereas some recipes call for whisking over hot water for the whole time until they’re super fluffy, others say you only have to heat the mixture at the start to about 40-45C before continuing whipping. We tried that last method. However, we noticed that the mixture doesn’t hold on to heat that well so that after less than a minute of removing it from the heat it had cooled down slightly again. We’re doubtful as to whether it actually helped.

A historical remainder?

It seems as if this step is a remainder of the days that we didn’t have electric mixers. It would have been very hard to incorporate enough air into these sponges. Anything to help hold on to and add extra air would have been welcome. Heat would have given just that extra bit of leverage to make it super foamy.

In our test though, we found that a slight heat just to remove the ‘cold’ from the ingredients (the eggs came straight from the fridge) was probably good enough. Would we use the step next time? Probably not, it’s just so much easier to leave them in a stand mixer for 10-15 minutes instead of standing next to a pan of boiling water.

Baking immediately

Once the flour and butter have been mixed through the whipped eggs you should bake the cake immediately. Don’t leave it on the counter for too long. The batter just isn’t strong enough to hold on to the batter by itself. The air won’t disappear immediately but it will slowly disappear from the cake.

Once you place the cake in the oven the eggs will start to cook, causing the proteins to denature and form a more solid like structure. Also, the gluten and starch in the flour will cook, air will expand and moisture will evaporate. Together, this will make the cake rise slightly and then become strong enough to hold on to the air by itself.

My Genoise has turned out very dense, not at all light and airy!

There are various possible reasons for this and thus a few strategies you can use to solve it:

  • Add less butter, especially if you’ve got a recipe with quite a lot of butter (like the one in this post). Butter tends to weigh down the mixture, making it harder to rise in the oven, but it can also cause more air escaping before you actually bake.
  • You may have been too harsh when folding in the flour and melted butter.
  • Your eggs may not have foamed up enough during whisking. Try adding a bit more sugar to firm up the foam a bit more.
Genoise cake with two layers
A double layer Genoise cake with jam in between. The cake is quite light in colour and is a lot lighter than a carrot or zucchini cake.

Storing this hygroscopic cake

Most Genoise cakes are decorated completed with buttercream, glazes, icings or at least something that closes them off from the outside. One of the reasons for this may be that the Genoise is very hygroscopic. In other words, it seems to absorb moisture and become sticky quite easily, it’s at least what we saw happening to ours.

Meringues are known to be hygroscopic as well, both the sugar and cooked egg tend to absorb moisture. Since the Genoise contains a lot of sugar and egg whites as well a very similar mechanism is likely to be occurring here. Therefore, either coat it completely with a nice decoration or store it in an air tight container, then it won’t have any additional moisture to absorb!

To end with: a note on sponge vs. cake

Before writing this post, I had no idea that there’s a difference between a sponge and a cake. And actually, it seems to depend who you ask whether there is indeed a difference and what this difference is exactly.

A definition seems to be that sponges do not contain any fat whereas cake contain fat. However, a Genoise contains fat (in most cases that is) and is still often called a sponge. To make it more confusing, there seems to be something like a sponge cake as well, a combination of the two.

If you have another definition, let me know. Here in this article we’ve used cake, referring to both sponge and sponge cake, whichever you prefer.

Sources

The cake bible, link

Laws of baking, on Genoise cakes, link

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