Cheesecake is a sweet dessert consisting of one or more layers. The main, and thickest, layer consists of a mixture of a soft, fresh cheese (typically cottage cheese, cream cheese, quark or ricotta), eggs, and sugar. If there is a bottom layer, it most often consists of a crust or base made from crushed cookies (or digestive biscuits), graham crackers, pastry, or sometimes sponge cake. Cheesecake may be baked or unbaked (and is usually refrigerated).