1/2 c. butter
3 sq. (1 oz. each) unsweetened chocolate
2 c. sugar
1 2/3 c. undiluted Carnation evaporated milk (large can)
1 tsp. vanilla

Melt butter and chocolate in saucepan on medium heat. Stir in sugar, then very slowly, add the evaporated milk, stirring with a wooden spoon so mixture does not burn. Heat to a gentle boil, stirring constantly. As soon as it boils, remove from heat. Cool a few minutes and add vanilla. Makes approximately 2 3/4 cups sauce.