Master Recipe 
One usually comes across fish stocks that are rather neutral, without much personality. What makes this rich, multidimensional stock different? The flavorful fish bones are seared lightly before any liquids are added, creating an additional layer of flavor. Use any non-oily fish bones, such as monkfish or red snapper. For a pure, well-flavored stock with no bitterness, thoroughly rinse the bones, heads, and trimmings, removing the gills and any innards. Once cooked, extract the fish cheeks, if present, to enjoy as a special snack!
MAKES 1-1/2 QUARTS (1.5 L) MILD STOCK OR 3 CUPS (750 ML) RICH STOCK
EQUIPMENT: A 6-quart (6 l) saucepan; a flat metal skimmer; a fine-mesh sieve; dampened cheesecloth.
2 pounds (1 kg) non-oily fish bones, heads, and trimmings (gills removed), cut up
1/4 cup (60 ml) extra-virgin olive oil
1 shallot, peeled and minced
1 medium onion, peeled and minced
1/2 teaspoon fine sea salt
3 bay leaves, halved and crushed
Bouquet garni: fresh celery leaves, thyme sprigs, and parsley sprigs encased in a wire-mesh tea infuser or bound in a piece of cheesecloth
1. Thoroughly rinse the fish bones, heads, and trimmings under cold running water, so that no blood remains and the water runs clear, about 5 minutes. Drain and set aside.
2. In the saucepan, combine the oil, shallot, onion, salt, and bay leaves. Stir to coat the ingredients with the oil and sweat—cook, covered, over low heat—until soft, about 5 minutes. Add the fish bones, heads, and trimmings, increase the heat to high, and cook, uncovered, for 5 minutes more.
3. Add the bouquet garni and 2 quarts (2 l) cold water to cover. Bring to a simmer and leave to simmer gently, uncovered, for 20 minutes, skimming regularly to remove any foam or impurities that could add bitterness to the stock.
4. Remove the pan from the heat and set aside for 10 minutes to allow any additional impurities to settle to the bottom.
5. Line the sieve with the dampened cheesecloth. Set the sieve over a large bowl and ladle—do not pour—the stock into the prepared sieve. Rinse the saucepan and return the strained stock to the pan. Taste the stock for strength. For a mild stock, use as is. For a rich stock, boil the liquid until it has reduced to 3 cups (750 ml). Let cool to room temperature, then transfer the stock to an airtight container. The stock will keep in the refrigerator for up to 3 days or in the freezer for up to 1 month.
NOTE: When straining stock, never pour the liquid from the vessel through the strainer, or you are likely to pour unwanted impurities into the stock. Rather, set the stock aside for at least 10 minutes, to allow the impurities to settle to the bottom, then ladle the liquid into a sieve lined with moistened cheesecloth.