2/3 c. butter
1 c. dark brown sugar
1/2 c. evaporated milk
3-4 c. confectioners' sugar
1 tsp. vanilla

Melt butter. Add sugar and milk. Bring to a boil, stirring constantly. Boil gently for 5 minutes. Stir in and beat 3-4 cups confectioners' sugar. Add vanilla; beat. Frost when of good spreading consistency.