It's the icing on the cake...or is it the frosting? When it comes to finishing and decorating favorite cakes, cupcakes, cookies, and other baked goods, when do you use icing and when do you use frosting—and what's the difference anyway?
To add to the confusion, you've probably heard the terms "frosting" and "icing" used interchangeably. However, there is a distinction between the two. In broad terms, frosting is thick and fluffy, and is used to coat the outside (and often the inner layers) of a cake. Icing is thinner and glossier than frosting, and can be used as a glaze or for detailed decorating.
The most popular kinds of frosting are traditional (or American) buttercream frosting, cream cheese frosting, Swiss meringue buttercream frosting, and and Italian meringue buttercream frosting. Traditional (or American) buttercream frosting is the classic birthday cake frosting. It's made with a mixture of fluffy creamed butter, confectioners' sugar, a small amount of liquid (usually milk) and flavoring such as vanilla, coffee or raspberry. Cream cheese frosting is made the same way as traditional buttercream, but with some of the butter swapped out for tangy cream cheese
Swiss meringue buttercream frosting begins by warming egg whites and sugar in a double boiler, after which you whip the mixture to shiny peaks, then beat in softened butter. This frosting is silky and stable; perfect for piping and decorating. Italian meringue buttercream frosting starts with a base of whipped egg whites, to which you add hot sugar syrup and then softened butter until the frosting is glossy and fluffy, and marshmallow-like.
At its most basic, icing can be a simple combination of confectioners' sugar and liquid (cream, milk, citrus juice, or liqueur) mixed to a smooth consistency that's thick enough to coat the surface of a cookie but thin enough to spread into a completely smooth, almost puddle-like layer.
Royal icing is the most popular kind of icing for detailed cookie decorating. It also contains confectioners' sugar and liquid, with the addition of egg whites or meringue powder, which gives the icing more stability and allows it to dry to a hard, shiny finish. Royal icing can act as an edible glue for assembling gingerbread houses, and can be made thinner or thicker depending on if you're using it for piping detailed decorations or for "flooding"—that is, filling in the surface of the cookie with a smooth, even layer of icing.