Melt 1 1/2 squares baking chocolate in 1 T. butter. Add 1/2 c. boiling water, stirring rapidly. Let boil up and thicken. Quickly stir in 1 cup sugar, 1/3 c. light corn syrup, and a pinch of salt. Return to a boil and simmer about 1minute. When cool add 1 t. vanilla. Serve warm or cold.