Melt butter in large frying pan - add pork, beef and cook until lightly browned. Yes,cook the lean meat in butter! Add onion, celery and garlic.  Cover and cook 10 - 15 minutes until celery is tender.  Remove from heat. Stir in sherry, grated cheese, salt and bread crumbs. Mix well. Stuff each shell with slightly cooled mixture and close. Pour some sauce into shallow casserole.  Arrange shells open side down and top with remaining sauce.    Baked covered at 375 for 30 minutes...   make enough for leftovers.....  they're even better the next day!