This section is from the book "The Illustrated London Cookery Book", by Frederick Bishop. See also: How to Cook Everything.
It must be understood that this stock will not keep long, three days being the utmost. Take two pounds and a half of English eels;, silver eels as they are termed, they may be known from the Dutch by the white silvery appearance of the belly; cut them in pieces about an inch and a half or two inches long, cut up six fresh flounders and a pound and a half of skate. Place them in the pan with sufficient water to cover them, add two heads of celery, three parsley roots cut in slices, an onion, and sweet herbs; season with pepper, salt, and mace. The onion should be stuck with cloves, and a little of the liquor from any potted fish will improve the flavour, but must not be added until just previous to serving; cover close down and simmer one hour and three quarters, strain off for use.
The only difference between this and brown soup is that the fish must be first fried brown in butter.
Fish soups may be most numerous; there is scarcely a fish which may not be used for this purpose, the most available and. easiest made are those which are composed of the cheaper kinds of fish.
To three quarts of good white stock, add fifty cray fish, having first picked off the tails, the meat from the head and shells, and beat to a paste in a mortar, it will become of the consistency of cream; boil it fifteen minutes, rub it through a tammy, or coarse cloth, season with salt and cayenne pepper: the colour may be heightened by lobster spawn, beat up with the meat of the cray fish, or the juice of beet-root.
Take any number of pounds of eels according to the quantity required; add two thirds water. If about three or four pounds of eels add one onion, a small quantity of mace, a little pepper whole, sweet herbs, a crust of the top side of bread, cover down close; stew till the fish separates, strain. Toast slices of bread deep brown but not to burn, cut into triangular pieces or squares, a piece of carrot two inches long cut into four slices lengthways, put into a tureen with the toast, pour the soup on, boiling cream may be added thickened with a little flour, but it should be rich enough without it.
Make stock of skate, flounders, and eels; cut some handsome cutlets from a turbot, salmon, or cod; lay them aside. Make a marinade composed of three turnips, the like number of carrots, two onions, and half a clove of garlic, the flavour of the last is alone desired; the quantity, therefore, may be just sufficient to communicate it, and no more: and then, according to the quantity of fish proposed to be cooked, add water, and one third wine, squeezing into it the juice of half a lemon. Stew this together for fifteen minutes, strain it, and let it get cold; then add the cutlets, simmer until the liquor is one third reduced, pour in the stock first made, thicken it with cream, season with a little cayenne and salt; serve up the cutlets in the dish with the soup.
 
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