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.