Place the potatoes and onion on a large piece of heavy-duty foil (about 20 in. x 20 in.); dot with butter. Combine the cheese, parsley, Worcestershire sauce, salt and pepper; sprinkle over potatoes. Fold foil up around potatoes and add broth. Seal the edges of foil well. Grill, covered, over medium heat for 35-40 minutes or until potatoes are tender.