Make cornbread according to package directions. Let cool, crumble and set aside. Boil sweet potato until tender. Mash, set aside. Remove sausage from skin and crumble, cook in frying pan and drain. Chop celery, onion and green onions. Saute with butter. Add the cooked sausage pieces to the skillet with vegetables. Add oysters, crumbled cornbread, parsley and mashed sweet potato. Mix well. Place in a 9 x 13-inch greased baking dish. Bake at 350˚F for 1 hour or bake with chicken or turkey until bird is fully cooked.