Boil a fish weighing four pounds in salted water. When done, remove the skin, and flake it, leaving out the bones. Boil one quart of rich milk. Mix butter size of a small egg with three table-spoonfuls of flour, and stir it smoothly in the milk, adding also two or three sprigs of parsley and half an onion chopped fine, a little Cayenne pepper, and salt. Stir it over the fire until it has thickened.
Butter a gratin dish. Put in first a layer of fish, then of dressing, and continue in alternation until all the fish is used, with dressing on top. Sprinkle sifted bread-crumbs over the top. Bake half an hour. Garnish with parsley and slices of hard-boiled egg.
As the rules for boiling, broiling, frying, cooking au gratin, and stewing are the same for nearly all kinds of fish, I will not repeat the receipts for each particular one. I will only suggest the best manner for cooking certain kinds, and will add certain receipts not under the general rule: