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

Combine sugar and cornstarch in saucepan. Blend in butter and boiling water. Add chocolate. Cook, stirring constantly, until chocolate melts and mixture becomes thick and smooth. Remove from heat. Blend in 1/2 tsp. vanilla. Cool to lukewarm. Frosts 1 eight or nine inch layer cake.