Sponge cakes are European-style cakes made with very little fat. They're featured in layer cakes, charlottes, jelly rolls, and tiramisu.
Unlike butter cakes and chiffon cakes, sponge cakes include little fat other than what's in the egg yolks. And because of their low fat content, homemade sponge cakes won't resemble a moist, cream-filled snack cake. But soaked with simple syrup and flavorings, they are delectable.
Sponge cakes also require some special treatment. For one, sponge cake batter waits for no one. So have all of your ingredients measured and sifted and ready to go in separate bowls. Accuracy is key: use a scale if you have one. Your cake pans should be greased and lined with parchment, and your oven preheated.
Sponge cakes are best made with an electric mixer -- preferably a stand mixer, so your hands are free.
Warming the Eggs
You'll also want to warm your eggs. Why? Because warmed eggs hold more air and create more volume when they're whipped than cold eggs. Here's how you do it:
- Set a stainless steel bowl over a pan of simmering water.
- Add a few tablespoons of sugar from the recipe into your egg whites, and whisk it in. Sugar has an insulating effect, and helps protect the eggs from coagulating over the heat.
- Keep whisking the eggs while you heat them, testing now and then with your fingertip until they feel warm to the touch.
Alternate Method: Hot milk sponge cakes use scalded milk to warm the eggs.
Whipping the Eggs
When the egg whites (or yolks -- whatever you're heating) are warm, transfer them to your mixing bowl and whip until medium-stiff peaks form. Stop beating the egg whites just when stiff peaks form: you don't want them to appear dry. Perfectly beaten egg whites will fold into batter without breaking apart into white flecks and islands, and the air bubbles will still expand in the oven.
Adding Volume: Whipping egg whites separately from egg yolks adds even more volume to a sponge cake batter. Beat your egg yolks with sugar until they're thick and lemon-colored; when you lift up the beaters, a "ribbon" should form on the surface as the mixture drops back into the bowl. Meanwhile, adding melted butter or sifted cocoa powder decreases the batter's volume, so fold these in very carefully.
Folding in Egg Whites
Use the "one-third, two-thirds" method for folding in egg whites:
- Add one-third of the beaten egg whites into the bowl of thick batter.
- For best results, use a balloon whisk -- one of the big bulbous ones -- stirring gently until the ingredients are incorporated and the batter is lightened. (A rubber spatula, plastic bowl scraper, or even your hands also work well.)
- Add the remaining egg whites to the batter, gently folding with smooth strokes through the center of the bowl, around the sides, and lifting through the center again, repeating until batter is smooth.
- Immediately divide batter into prepared pans, smoothing the surface if necessary, and transfer them to the hot oven.
- Bake as directed.