1/4 lb. butter
4 (1 oz.) squares semi-sweet chocolate
2 1/2 c. white sugar
1 (13 oz.) can evaporated milk
1 tsp. vanilla

Melt butter and chocolate in top of double boiler over boiling water. Add sugar and evaporated milk alternately about 1/4 cup at a time, stirring constantly. When all sugar and milk have been added, reduce heat to medium and heat for 10 minutes until sauce begins to thicken. Stir occasionally. Remove from heat. Add 1 teaspoon vanilla. Cool. Makes 1 quart.