Fish stock is the starting point for all good seafood soup recipes.
You can make fish stock with just about any kind of fish and they will all taste relatively the same, but I suggest you avoid using fatty fish like bluefish, tuna, or salmon. My personal favorite fish for a fine stock is tautog, but you can also use fluke, sea bass, cod, or haddock. Just make sure you remove any innards from the racks, and if you choose to include the fish heads, remove the gills, which supposedly can result in a bitter-tasting stock. I generally skip using the heads, instead opting for the backbones, ribs and fins, which contain a fair amount of gelatin and help thicken the consistency of the final product.
I’ll often make up a large batch of fish stock in the spring, and freeze it for later use in quart-sized zipper bags.
FISH STOCK
2 tablespoons olive oil
1 large onion, chopped
2 carrots, chopped
2 celery ribs, chopped
2 bay leaves
2 pounds bones and trimmings from fish racks
8 cups water
4 whole black peppercorns
2 teaspoons salt
Heat oil in a heavy 5-quart pot over moderately high heat until hot but not smoking, then sauté onion, carrots, and celery, stirring occasionally, until golden, 6 to 8 minutes.
Add fish bones and trimmings, water, peppercorns, bay leaves and salt, and bring to a boil, skim off the froth, then reduce heat to low and simmer, uncovered, for around 30 minutes.
Pour stock through a fine-mesh sieve into a large bowl, and discard the leftover solids.