4 pounds fish bones (from white fish only), heads, fins, and gills removed, and bones rinsed well
2 cups shrimp, crab, or lobster shells (optional)
1 large onion (about 1 pound), peeled and quartered
2 stalks celery, cut into 1-inch lengths (about 1 cup)
1 large carrot, peeled and cut into 1-inch lengths (about 1 cup)
1 whole head of garlic, cut crosswise
Fennel stalks cut from 1 fennel bulb (see fennel below), cut into 1-inch lengths (about 8 ounces)
1 stalk lemongrass (about 1 ounce), cut into ½-inch rounds
1 teaspoon fennel seeds
Bouquet garni, made with 1 bay leaf 3 sprigs parsley and 3 sprigs fresh thyme tied in cheesecloth
¼ teaspoon whole black peppercorns
Cod and vegetables:
1 bulb fresh fennel, cut lengthwise into sixths, fronds reserved for garnish and tops reserved for the stock
2 carrots, peeled and cut into 1-inch lengths
6 small potatoes, peeled and halved
6 6-ounce cod fillets
Sea salt and freshly ground black pepper to taste
Make the fish stock:
In a large stockpot, combine all the ingredients. Bring to a boil over high heat. Reduce the heat and simmer for 45 minutes, partially covered. Skim any impurities that rise to the top several times during cooking. Strain the stock through a fine-mesh sieve. (You should have approximately 3 quarts.)
Prepare the cod and vegetables:
Put the fish stock in a large stockpot and bring it to a boil. Add the fennel wedges, carrots, and potatoes, reduce the heat, and simmer for 15 minutes. Remove the vegetables from the stock with a slotted spoon and place in a bowl.
Bring the stock back to a high simmer and add the cod pieces. Poach for 8 to 10 minutes until the cod is flaky and opaque. Return the vegetables to the pot and cook for 2 minutes. Remove the pot from the heat.
To serve, place 6 large soup bowls on the counter near the stove.
Place a variety of vegetables in each bowl, Then place a piece of cod in the center of each bowl along with the vegetables.
Ladle some of the hot broth over the fish and vegetables. Sprinkle with sea salt and freshly ground pepper.
Chop 1 tablespoon of fennel fronds and garnish each bowl with some chopped fennel fronds. Serve immediately.
If you are not on a diet, serve the cod with garlic aioli . For a sublime flavor pairing with cod, add one quarter teaspoon of saffron to the aioli.
Don’t get scared off by having to make fish stock. The homemade variety is worth the trouble and brings the soup to life. When making a fish stock, always rinse the bones well; remove gills and any extra skin since they will discolor the stock. I use bones from white fish, and if I have any shrimp, crab, or lobster shells I add them for extra flavor. Most fishmongers will sell or give you fish bones if you ask them in advance. If the fish stock is not to be used within 24 hours, cool it and freeze for up to three weeks.
Once a friend from the south told me you should never cut fish on wood or cook with wooden utensils because it spoils the fish, and I haven’t since. Maybe it’s because the fish will pick up flavors from the wood, I don’t know for sure.