Dice onion, potato, celery and lamb into cubes of approx 1cm.
In a large bowl combine the lamb, onions, potatoes, celery, garlic, parsley and mix well.
Cut pastry in half and fill with mix, sealing the edges with egg wash, form into a pastie shape. Also baste the surface of the pastie with egg wash and bake at 200C for 45 minutes.