To remove the scales hold the fish by the tail and scrape firmly toward the head with a small sharp knife, held with the blade slanting toward the tail. Scrape slowly so that the scales will not fly, and rinse the knife frequently in cold water. If the fish is to be served whole, leave the head and tail on and trim the fins; otherwise remove them.
TO OPEN FISH
To open small fish cut under the gills and squeeze out the contents by pressing upward from the middle with the thumb and finger. To open large fish split them from the gills halfway down the body toward the tail; remove the entrails and scrape and clean, opening far enough to remove all the blood from the backbone, and wiping the inside thoroughly with a cloth wrung out of cold, salted water.
TO SKIN FISH
To skin a fish remove the fins along the back and cut off a narrow strip of the skin the entire length of the back. Then slip the knife under the skin that lies over the bony part of the gills and work slowly toward the tail. Do the same with the other side.
TO BONE FISH
To bone a fish clean it first and remove the head. Then, beginning at the tail, run a sharp knife under the flesh close to the bone, scraping the flesh away clean from the bone. Work up one side toward the head; then repeat the same process on the other side of the bone. Lift the bone carefully and pull out any small bones that may be left in the flesh.
BOILED FISH
To cook fish properly is very important, as no food, perhaps, is so insipid as fish if carelessly cooked. It must be well done and properly salted. A good rule to cook fish by is the following: Allow ten minutes to the first pound and five minutes for each additional pound; for example: boil a fish weighing five pounds thirty minutes. By pulling out a fin you may ascertain whether your fish is done; if it comes out easily and the meat is an opaque white, your fish has boiled long enough. Always set your fish on to boil in hot water, hot from the teakettle, adding salt and a dash of vinegar to keep the meat firm; an onion, a head of celery and parsley roots are always an acceptable flavor to any kind of boiled fish, no matter what kind of sauce you intend to serve with the fish. If you wish to serve the fish whole, tie it in a napkin and lay it on an old plate at the bottom of the kettle; if you have a regular "fish kettle" this is not necessary. In boiling fish avoid using too much water.
To thicken sauces, where flour is used, take a level teaspoon of flour to a cup of sauce, or the yolk of an egg to a cup of sauce.