This light, airy cake gets its ethereal texture from beaten egg whites, which are folded into a fluffy mixture of beaten egg yolks and sugar. They get their leavening power entirely from eggs. Sponge cakes are further characterized by the fact that they do not contain shortening of any kind. The cakes can be variously flavored with anything from lemon to ground almonds.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.