Fish stock forms the base for multiple dishes, including hearty cioppino, delicate poached flounder and classic bouillabaisse. Unlike chicken or beef stocks, which may simmer for hours, fish stock traditionally takes just 20 to 30 minutes of cooking to extract flavor from the bones. You can cook fish stock longer, though, if you're not using flat fish bones, and still get flavorful results.

Obtain fish bones from raw fish at the grocer's fish counter. Use flat-fish bones from fish such as flounder or sole if you want a short cooking, delicately flavored stock. These bones turn a broth bitter if you cook them too long. Opt for bones and heads from white fish, such as snapper or cod, for a longer-cooking, more robust stock. Avoid bones from oily fish, such as mackerel or salmon, which will create an oily stock. Clean any remaining blood from the bones too; blood leads to a cloudy, bitter stock.

Peel and chop the leeks or onions, celery, carrots and any aromatics -- stems and all. Place them in a large, deep pot with the fish bones. Add a few bay leaves and whole black peppercorns, as well as a generous pour of dry white wine.

Cover the stock ingredients generously with water, and place the pot over medium heat. Bring the liquid to a simmer; skim off any foam that rises to the top. Allow it to cook for 20 to 30 minutes, if you have flat fish bones, or up to 6 hours for other fish bones. Periodically remove any scum from the top of the stock.

Remove the pot from the heat and allow the stock to cool slightly. Strain through the fine-mesh strainer or cheesecloth. Discard the bones and vegetables. Refrigerate it for up to three days, or freeze the stock for later use. Frozen stock stays fresh for approximately one month.