Chop and lightly fry the onion. Line 12 small round tins or small saucers with half the pastry. Mix together the minced mutton, chopped onion, chopped mushrooms, parsley, thyme and seasoning. Divide the mixture between the tins. Add to each alittle stock to moisten. Cover with lids made from the rest of the pastry. Brush with egg or milk and bake in a moderate oven (350° F., Gas 4) for about 30–45 min.