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 minutes or until candy thermometer reaches 234 degrees 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.
