Peel and thinly slice potatoes. Mince parsley, slice onion. Place Potatoes and onion on a large piece of heavy duty foil with butter. Combine cheese, parsley, worcestershire sauce, salt and pepper: sprinkle over potatoes. Fold foil up around potatoes and add broth. Seal edges of foil well. Grill, covered, over medium coals for 35-45 minutes or until potatoes are tender.