Combine Chocolate, Margarine And Corn Syrup In Medium Saucepan With Silver- Stone. Stir Over Low Heat Until Melted And Smooth. Remove From Heat . Stir In Vanilla Extract And Sugar. Add Rice Krispies Mixing Lightly Until Coated. Spread Evenly In 13X9 X2 Pan . Chill Until Firm. Cut Into 1 1/2 Inch Squares. Store In Refrigerator. Makes 48 Squares.