This is a creamy delicious, easy to make frosting for any cake or cupcake recipe. This is also an ideal frosting to use for the crumb coat under rolled fondant; it has a good consistency for spreading, and provides a firm base for the fondant. When dry it forms a thin crust, but is still soft enough to enjoy when eating. Shortening makes the frosting more stable and reduces the tendency to melt in warm weather. Butter gives this frosting a rich and luscious taste, but using butter and vanilla extract produces a frosting that is not pure white. For a whiter frosting use clear vanilla extract. For a pure white frosting, omit the butter and increase the vegetable shortening to 1 cup along with clear vanilla extract. I've never liked the thought of eating a pure shortening frosting, but it does produce a snowy white frosting if this is what is desired. This recipe makes about 3 cups of frosting, enough to fill and frost a 9" two layer cake. For large cakes increase the recipe by 1½ or 2 times. A recipe like this is very forgiving. If you feel you don’t have enough to finish your cake, just add a little more butter or shortening, and a little more powdered sugar plus enough milk for the right consistency.