1/2 c. butter
4 squares (1 oz. each) baking chocolate
3 c. sugar
1 (12 oz.) can evaporated milk
1/2 tsp. salt
1 tsp. vanilla extract

Melt butter and chocolate together in top of double boiler over hot water. Gradually add sugar. Add slowly, stirring constantly, the evaporated milk. Add salt and vanilla extract.

Continue cooking until the sauce thickens, stirring occasionally, about 1 hour. Remove from heat. Cool. Store in refrigerator.