When choosing bones for fish stock, it's very important to choose low-activity fish carcasses. With increased activity (often predatory fish, such as salmon) comes stronger flavor and higher oil content. For a delicate stock, you want fish that hang out at the bottom and move as little as possible (such as sole, flounder, or other flatfish). This recipe is based on one taught at the Culinary Institute of America, and it's a keeper. It has great flavor and, almost as important, it's adaptable. —Derek Laughren
4 1/2 quarts
onion, 2" dice
celery, cut on a bias in 2" lengths
parsnip, cut on a bias in 2" lengths (peeling optional)
leek, cleaned well and cut in 2" dice
black peppercorns, coarsely crushed with a heavy pan
Sweat your mirepoix (onion, celery, leek, and parsnip) in a 6 quart or larger stock pot (no oil). After a couple of minutes, once the onions are softened and the vegetables are fragrant, add in the bones and stir together gently.
Add the parsley, thyme, pepper, bay, and crushed garlic. Add the water. Bring to a gentle simmer and cook for 45 minutes. As scum floats to the top and gathers in clumps, skim and discard.
Using tongs for the larger carcasses and a spider for vegetables, remove as much as possible from the stock. Hang a fine mesh strainer over a 6 qt or larger bowl. Run a double layer of cheesecloth under cold water and use it to line the strainer. (This will keep the cheesecloth from moving around on you when you pour.) Carefully pour the stock through the strainer, stopping if it begins to back up. You can tap a wooden spoon against the handle of the strainer quickly and repeatedly to speed up the straining process.
Use as much as you need and freeze the rest for next time!