Scald ¾ c. milk in top of double boiler. Add ¼ c. sugar, 2 tblsp. flour and ⅛ tsp. salt, and blend. Add 1 egg, slightly beaten. Cook over boiling water 5 minutes, stirring constantly. Blend in 2 squares unsweetened chocolate, melted. Cover and cook 5 minutes longer, stirring occasionally. Chill. Whip ½ c. heavy cream and add 1 tsp. vanilla. Fold into chilled mixture.