To make the stuffing

• Melt the butter in a frying pan, add the chopped onion and celery and cook until soft.
• Crumble the Christmas pudding into the pan and mix with the onion and celery, add the chopped nuts and season with salt and pepper.
• Leave to cool, then add the egg yolk to bind the stuffing together.
• Stuff the bone cavity of the lamb with the pudding stuffing mixture and tie up with string or secure with cocktail sticks.
• If there is any stuffing left over it can be cooked separately in an ovenproof dish.
• Heat the oil in a roasting tin and brown the lamb on all sides. Add the shallots to the tin.
• Roast at 180C (375F) for about 1 1/2 hours for pink lamb, 1 3/4 hours for well-done meat.
• Transfer the lamb to a warm platter, cover with foil and leave to rest in a warm place.
• Put the shallots, lamb stock and any juices from the lamb in a small pan and puree with a hand blender, add the redcurrant jelly and warm through
• Carve the lamb with the pudding stuffing with roasted vegetables and the shallot &redcurrant jelly gravy.