Betty Crocker and Martha Stewart both have easy-to-make white frosting recipes. The Betty Crocker version has a rating of 4 stars out of 5 stars, and the Martha Stewart recipe rates 3 stars out of 5 stars. Both recipes make 12 servings, enough to frost a normal cake.
To make the Betty Crocker version of white frosting, get a medium bowl and mix 3 cups of powdered sugar with 1/3 cups of softened butter with an electric mixer at low speed. Stir in 1 1/2 teaspoons of vanilla and 1 to 2 tablespoons of milk in order to make the frosting spreadable and smooth. If the frosting is too thick, add more milk, a couple of drops at a time. If the frosting is too thin, add small amounts of powdered sugar until it is at the right thickness.
Martha Stewart's recipe for white frosting is similar, but only uses confectioner's sugar, milk, which is optional, and butter. For this recipe, take 1 1/2 sticks of unsalted butter and allow it to soften. Cream the butter in a bowl until smooth, and then gradually begin to add the sugar, stirring with each new addition. If the frosting becomes too thick, begin adding the milk until the frosting has the correct consistency.