Combine sugar, salt, cream, corn syrup and chocolate. Cook over low heat, stirring until sugar dissolves. Cover saucepan for 2 or 3 minutes. Remove lid and cook to the soft ball stage (234°). Beat to spreading consistency. Add a little hot water if frosting becomes too stiff to spread evenly, sifted confectioners sugar if too thin. Frosts sides and top of three 8" layers