Easy Powdered Sugar Icing 2 cups powdered sugar (sifted) 1/2 teaspoon vanilla 2 tablespoons milk Mix the powdered sugar with the vanilla and milk. Then add more milk a bit at a time until it is thin enough to drizzle over a cake. Once you've iced your cake, it's best to let it stand for one or two hours. To make chocolate icing, add two tablespoons cocoa powder when you mix the powdered sugar and follow the rest of the recipe above.