1/2 c. sugar
1 1/2 tbsp. cornstarch
1 (1 oz.) sq. unsweetened chocolate
Dash of salt
1/2 c. boiling water
1 1/2 tbsp. butter
1/2 tsp. vanilla

Mix sugar and cornstarch, add salt and chocolate. Add water, cook until mixture thickens. Remove from heat, add butter and vanilla. Spread on cake while for a glossy frosting which remains soft and smooth and not too rich.