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