This section is from the book "The Complete Cook", by J. M. Sanderson. Also available from Amazon: The Complete Cook.
The head and shoulders, comprehending in weight two-thirds or three-quarters of the fish, is much better dressed separately; the tail being much thinner would be broken to pieces before the thicker parts are done. The best way of dressing the tail, is to fry it. For boiling cod, allow plenty of room and water, that the fish may be perfectly covered. Put it in blood-warm water, with a large handful of salt. Watch for its boiling, that it may be set a little aside. A small cod will require twenty minutes after it boils; a large one, half an hour. When the fins pull easily, and the eyes start, the fish is done. Slip it very carefully on the fish plate, that it may not be broken. Take out the roe and liver, which are much esteemed; they will serve to garnish the dish, together with horse-radish and slices of lemon, or fried smelts, or oysters. Sauce, oyster. The sound, a fat jelly-like substance, along the inside of the backbone, is the great delicacy of the fish. Cod is sometimes boiled in slices. Let them be soaked half an hour in salt water; then set on with cold spring water and salt, just enough to cover them. Let it boil up; then carefully skim and set aside for ten minutes. Serve with the same sauce as above. Slices of cod are much better fried as soles. Slices of crimped cod, for boiling, are put in boiling water, and when done served on a napkin.
196. Ling is a large fish, somewhat resembling cod, and may be dressed in the same way, but is very inferior in quality.
197. Haddock is but a poor fjsh, make the best of it. It may be boiled, and served with egg sauce, but it is better stuffed, and baked or broiled, and served with good gravy, or melted butter, flavoured with anchovy or mushroom catsup.
198. Whitings may be skinned or not. Fasten the tail to the mouth; dip the eggs and bread crumbs, or oatmeal, and fry as soles; or they may be cut in three or four pieces, and fried. They do not take long to fry; not more than five minutes; but several minutes should be allowed to drain the fat from them, as the beauty of them is to be perfectly dry. Sauce, anchovy, or parsley and butter.
 
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