3 oz. unsweetened chocolate
3/4 c. sugar
3/4 c. boiling water
3 tbsp. cornstarch
1/8 tsp. salt
1/4 c. water
1 tsp. water
1 tsp. butter

Melt chocolate in double boiler. Mix in sugar. Slowly stir in 3/4 cup boiling water. Combine cornstarch, salt, with 1/4 cup water. Stir into chocolate mixture. Cook over direct heat until mixture boils and thickens, stirring. Cook over hot water, covered, 10 minutes. Add butter and vanilla. Cool.