Sponge Cakes

Sponge cakes are cakes made by beating whole eggs, separated eggs, or just egg whites with sugar and then folding the beaten mixture with butter or flavorful ingredients such as chocolate. Last, flour and/or other dry ingredients are folded with the egg mixture. If the cake is based on beaten egg whites instead of whole eggs, the beaten egg yolks are also folded into the mixture. One of the best-known sponge cakes, called biscuit (pronounced bees-kwee), is made by beating egg yolks and egg whites separately, each with sugar, and then folding the two mixtures together while sifting flour over them. American sponge cakes are made in the same way as biscuit except that they usually contain slightly more egg. A whole-egg sponge cake, called a genoise, is made by beating whole eggs with sugar until the eggs quadruple in volume and then sifting the flour over them while folding it in. Most recipes also call for folding in a small amount of melted butter. Both of these cakes, while light and airy, tend to be dry. Because of this, European bakers brush each layer liberally with simple syrup flavored with some kind of fruit brandy, rum, or coffee while stacking them; the cake ends up moist, almost wet. One advantage of this method is that you can moisten cakes that are a little stale (whether from being held too long or from being frozen), so you can bake cakes ahead of time, wrap them in plastic, and freeze them. Both kinds of sponge cakes are leavened only with the air beaten into the eggs. They contain no baking powder or baking soda.