Use this White Confectioners' Sugar Icing recipe to decorate our White Sheet Cake.
Cream butter and sugar in the bowl of an electric mixer fitted with the paddle attachment until well combined. Add salt, vanilla, and milk, and beat until frosting is smooth and creamy. If icing seems too thick, add an additional tablespoon of milk. Use immediately, or refrigerate for up to 2 days. Bring to room temperature before frosting cake. Return to mixer until creamy if necessary.