1/2 c. butter (no substitutes)
1 (4-oz.) sweet chocolate bar, chopped (Baker's German Sweet)
1 c. sugar
1 can (5-oz.) evaporated milk
1 Tbsp. light corn syrup
1/8 tsp. vanilla extract

Melt butter and chocolate in a heavy saucepan over medium-low heat. Stir in sugar, evaporated milk, corn syrup, and salt; cook over medium heat, stirring gently, 5 minutes or just until sugar dissolves and sauce is smooth. Remove from heat; stir in vanilla. Serve warm.