In a mixer with a whisk attachment, cream the butter for about a minute on medium speed.
Slow the speed to low and gradually add the powdered sugar. Stir in the vanilla and 1 tablespoon of milk. You want the frosting to be a smooth consistency.
Depending on the thickness of the frosting, add more milk in small amounts at a time.
If the frosting is too thin, add in small amounts of the powdered sugar.
This recipe makes enough frosting for an 9 inch layer cake or an 13 x 9 inch cake.