To make powdered sugar icing, mix together 3 cups powdered sugar and 1/3 cup softened butter, then add 1 1/2 tablespoons vanilla and 1 tablespoon milk. If necessary, add up to another tablespoon of milk until the frosting is smooth.
If the frosting is too thick, continue to add milk until it thins out. If the frosting is too thin, add more powdered sugar until it thickens. This recipe creates enough frosting to use on a 13-by-9-inch cake or an 8-inch layer cake. To make a chocolate powdered sugar frosting, add 1 to 2 tablespoons cocoa powder to the mixture. For other flavors, add lemon juice or almond extract, or add food coloring to make colored frosting.
Besides powdered sugar icing, there are other methods to make frosting for cakes and other desserts. To make a cream cheese icing, beat together 6 tablespoons softened cream cheese and 6 tablespoons softened butter using an electric mixer. Slowly beat in 1 1/3 cup powdered sugar until smooth.
For a marshmallow frosting, put 2 cups whipping cream, a bag of mini marshmallows, 1 cup sugar and 1/8 teaspoon salt in a saucepan and heat over medium-low heat until the marshmallows are melted. Add in 1 to 2 teaspoons vanilla and refrigerate the frosting. Beat the chilled frosting with an stand mixer until smooth.