Cut the fish, the potatoes, and the onion into slices. Cut the pork into half-inch dice. Put the pork and the onion into a pan and saute them a light brown. Place in alternate layers in a large saucepan first potatoes, then fish, then pork and onion; dust with salt and pepper, and continue in this order until all the materials are used. Cover the whole with boiling water and let the mixture simmer for twenty minutes. Scald a pint of milk or of cream, take it off the fire and add one and a half tablespoonfuls of butter and three broken ship crackers or the same quantity of water biscuits. Arrange the fish mixture in a mound on a dish, cover it with the softened crackers, and pour over the whole the hot milk.