Beat 1/2 lb. unsalted unsalted butter until fluffy.

Add and beat in 1 1/2 lb. confectioner's sugar.

Add :

3 T. milk
1-2 T. pure vanilla

Variations: substitute some milk with orange juice and rind
                     omit 1 T. of milk and vanilla and substitute Grand Marnier or Kahlua
                     substitute other flavorings for vanilla, such as lemon or almond
                     dissolve instant coffee in the milk for a light coffee flavor