Heat the oil in a pan and cook the beef for 4-5 minutes until browned. Transfer to a large ovenproof casserole dish and add the celery, carrots, swede and parsnips. Pour over the beer or stock and the Worcestershire sauce. Cover and cook in the oven for 2 hours, or until the beef is tender.
Meanwhile make the dumplings; in a large bowl mix together the flour, suet, mustard and water.
Mix together to form a smooth dough and divide into 8 golf-size balls.
20 minutes before the end of the cooking time remove the casserole from the oven, thicken with the gravy granules then place the dumplings on top.
Cook uncovered for the remainder of the cooking time.