Combine
butter and brown sugar over low heat until sugar is
dissolved. Add the milk and return to the heat and
allow to come to a boil. Remove heat and allow to
cool to lukewarm. Add the vanilla and the powdered
sugar and beat to desired consistency. You may add
more powdered sugar if the icing is too soft or more
milk if it is too firm. Makes icing for an 8" layer
cake or 8x13" sheet cake.