Royal icing is the sweet hardened decor you find ... Recipes usually call for confectioners' sugar when it requires a form of sugar that will easily dissolve and won't produce a grainy texture ...
Note: If you are icing a 3-layer cake, use the following recipe proportions: 1 1/2 cup unsalted butter, 8-10 confectioners' sugar, 3/4 cup milk, and 1 tablespoon vanilla extract. Recipe from More ...