Preheat oven to 275-300 degrees. Place shoulder in large open roasting pan. Cook slowly in warm oven 4-6 hours. Season with salt and pepper and add chopped onions about 2 hours before done. Cover with foil at the time you add onions. Lamb should pull easily from bones when done. Serve as pulled lamb with mashed potatoes with onions and drippings as sauce. Can be made a day ahead, but pulling lamb is easier when lamb is still warm. Pulled lamb can be used for other recipes such as shepherd’s pie or as filling for ravioli.