A layer cake or sandwich cake is a cake consisting of multiple stacked sheets of cake, held together by a filling such as frosting, jam, or other preserves. Most cake recipes can be adapted for layer cakes; butter cakes and sponge cakes are common choices. Frequently, the cake is covered with icing, but sometimes, the sides are left undecorated, so that the filling and the number of layers are visible. Popular flavor combinations include German chocolate cake, red velvet cake, Black Forest cake, and carrot cake with cream cheese icing. Many wedding cakes are decorated layer cakes.