This recipe uses a technique called "sweating" to extract maximum flavor from every ingredient. Although sweating adds a step, this stock is still effortless to make and takes only five minutes longer to cook than the Traditional Fish Stock.
I begin by sautéing a very thinly sliced mirepoix (onions, celery, and carrots) with herbs and peppercorns. I then layer fish heads and frames (bones) on top of these vegetables, add a little white wine, and cover the pot. As the heads and bones "sweat" (and steam), the proteins are drawn out. If you peek, you will actually see little white droplets of flavorful protein coagulating on the surface of the bones. After the sweating is completed (about 15 minutes), I cover the bones with water and simmer them briefly. I let the mixture steep for 10 minutes before straining it, producing a stock that is full-flavored and gelatinous. The fish heads are what endow this stock with its marvelous jellied consistency, which in turn gives a luscious mouth feel to the chowder broth.
Strong Fish Stock can be used in any fish chowder, using 1 or 2 heads form haddock or cod mixed with any combination of flounder, sole, bass and/or halibut frames (bones).
You can employ the "sweating" method with any fish you use to make a chowder — simply substitute the same amount of heads and bones. Keep in mind, however, that while the heads and bones of salmon, bluefish, and other species of oily fish make a stock that is right for their own chowders, its flavor is too pronounced to be suitable in other chowders or soups.
For equipment, you will need a 7- to 8-quart heavy stockpot with a tight-fitting lid, a wooden spoon, a ladle, and a fine-mesh strainer.
