Spongecakes

Like the génoise, the spongecake is made from many eggs and little or no fat. The major difference between the two is that for a spongecake, the eggs are always separated to develop two foams, one from the yolks; the other from the whites, whereas for a génoise, the foam is made by whippping whole eggs. The spongecake’s final grain and texture are influenced by how much air is whipped into both the yolks and the whites.

These cakes are called cold-method sponges because you don’t warm the eggs in a warmwater bath before you whip them, as you do to make a génoise. Spongecakes are leavened exclusively by the two natural leavenings. One form of leavening comes from whipping air into the yolks and whites to form millions of air bubbles; the other leavening agent is the steam, which evaporates from the liquid of the eggs and passes through air bubbles, expanding them and developing volume in the cake.