Line 13 x 9-inch baking pan or two 8-inch-square baking pans with foil. Combine sugar, evaporated milk, butter, and salt in 4- to 5-quart heavy-duty saucepan. Bring to a full rolling boil over medium heat, stirring constantly. Boil, stirring constantly, for 4 to 5 minutes. Remove from heat. Stir in marshmallows, morsels, nuts, and vanilla extract. Stir vigorously for 1 minute or until marshmallows are melted. Pour into prepared pan(s). Refrigerate for 2 hours or until firm. Lift from pan; remove foil. Cut into pieces. Store tightly covered in refrigerator. Makes 4 pounds or 48 two-piece servings.