In an electric mixer, cream the butter and shortening until smooth and well blended.  Add the extract.  With the mixer on low speed, gradually beat in the sugar.  Scrape down the sides of the bowl and beater.  Add the milk and beat on high speed until frosting is light and fluffy.  Add l or 2 tablespoons more milk if too dry.  Cover the icing with plastic wrap to prevent drying until ready to use.  Store it in a covered container in the refrigerator for up to 2 weeks.  Whip before using.

Tint portions of frosting with desired food color (I use the food color that is a paste - available at cake decorating stores and party stores).

To make a Chocolate Frosting prepare the above recipe but beat in finished icing 8 ounces unsweetened chocolate (melted), plus 2 tablespoons milk.