1/2 c. butter
1/4 c. milk
1 c. firmly packed brown sugar
Powdered sugar (about 3 c.)
1 tsp. vanilla

Melt butter, add brown sugar and cook over low heat until mixture boils. Cook for 2 minutes, stirring continually. Add milk and keep stirring until mixture comes to a boil again. Remove from heat and add powdered sugar. Beat with electric mixer. Mix in vanilla; spread.