Cooked Icing

• Basic icing is limited to a relatively stiff texture, and the powdered sugar leaves it slightly grainy even when it's well made. Cooked icings typically boil the sugar into a candy-like syrup, giving a smoother and more elegant texture to the finished product. It also provides the opportunity to use ingredients such as vanilla beans or real chocolate, which can be tricky to mix evenly into an uncooked icing. Some cooked icings are used primarily as glazes, poured over the cake while still slightly warm. Others are cooled to room temperature and then spread over the cake by hand.

Boiled Icing

• Old-fashioned boiled icing is one example of a cooked chocolate icing that works primarily as a glaze. The ingredients and method are similar to those for fudge, and most recipes produce a thin icing with a delicate sheen and a slightly grainy texture. The ingredients are simmered together until they reach the soft-ball stage, which occurs at 235 to 240 degrees Fahrenheit. Then the mixture is cooled until it reaches 120 F, still soft but well thickened. At this point it can be beaten with an electric mixer until it loosens into a thick liquid and can be poured onto the cake.

Meringue-Based Buttercreams

• Italian buttercream is also sometimes called "boiled icing," because it's made with a boiled sugar syrup. The syrup serves the dual purpose of sweetening the icing and cooking the whipped egg whites, giving a stable and food-safe foam. Then butter and melted chocolate -- for a chocolate icing -- are slowly whipped into the mixture, until it comes to room temperature. The meringue loses a lot of its volume, but the end result is still a remarkably light and fluffy icing suitable for use on sponge or chiffon cakes. Swiss buttercreams take a slightly different approach, as you heat the egg whites and then slowly add the sugar, but are cooled and used in the same way.

Ganache

• Although it isn't precisely cooked, ganache is another type of chocolate glaze that can be used on cakes. It's made by adding chopped, high-quality chocolate to hot cream, and then stirring it until the chocolate melts completely and reaches a smooth, even consistency. For glazing purposes, use equal quantities of chocolate and cream by weight. Cool the ganache until it's just barely warm, then pour it carefully over the cake. If it's too warm, it will run down the sides without properly covering the top.