3 squares unsweetened chocolate
1/4 c. butter
1 1/2 c. confectioners' sugar
1 can evaporated milk

Combine all the ingredients in the top of a double boiler. Cover and heat over boiling water. Stir well. Cook 30 minutes, stirring occasionally. This keeps well in the refrigerator. Re-heat it in the double boiler when you want to use it again.