Brown the lamb in batches in a little oil and then put it into a deep ovenproof frying pan with a lid. Brown the onions in a little more oil followed by the carrots and add these to the lamb. Tuck in the bay leaves. Add the flour to the browning pan and stir for 2 minutes then add the stock, bring to a boil and scrape the base well. Shake in Worcestershire sauce and season, tip onto the lamb. put a lid on and cook for 1½ hours. Layer the swede on top, seasoning as you go and dot butter over the top. Put the lid back on and cook for 20 minutes. Grill to brown up the top before serving scattered with parsley.