How-to Make a Sponge Cake
Beat egg yolks in a mixing bowl until they begin to thicken. Gradually add 3/4 cup sugar, beating until the mixture is lemon-colored. Blend in flavorings. Sift together flour and salt
In another mixing bowl, beat egg whites on medium speed until soft peaks form. Gradually add sugar, beating on high until stiff peaks form.
Spoon a fourth of the egg white mixture into the yolk mixture