Using a stand mixer or hand mixer, whip the butter for about 2 minutes at medium speed. This step helps to aerate the butter and create a fluffy frosting.
Mix in the vanilla extract and 2 tablespoons of milk to start.
Beat in the powdered sugar 1 cup at a time at low speed until frosting is smooth. Add more milk if the frosting is too thick, or more powdered sugar if too thin.
Wait until your cake or cupcakes have completely cooled before frosting.
