Line 9-inch square pan with foil, with ends of foil extending over sides of pan; set aside.

Place sugar, butter and evaporated milk in large heavy saucepan. Bring to full rolling boil on medium heat, stirring constantly. Boil 4 min. or until candy thermometer reaches 234°F, stirring constantly to prevent scorching. Remove from heat.

Add chocolate and marshmallow creme; stir until completely melted. Add walnuts and vanilla; mix well.

Pour immediately into prepared pan; spread to form even layer in pan. Let stand at room temperature 4 hours or until completely cooled; cut into 1 inch squares.

Store in tightly covered container at room temperature. Makes 3 lb. or 40 servings, about two squares each.