Also called icing, this sweet, sugar-based mixture is used to fill and coat cakes, pastries, cookies, etc. In addition to sugar, frosting can contain a combination of other ingredients including butter, milk, water, eggs and various flavorings. It can be cooked (as with boiled icing) or uncooked (as with buttercream), and can range from thick to thin. The main requirement for frosting is that it be thick enough to adhere to the item being coated, yet soft enough to spread easily.