To Market, to Market

• If you live in a coastal region you can probably harvest your own mussels, but it isn't necessarily your best bet. Mussels are siphon feeders, whose bodies accumulate any contaminants that might be present in your local waters. That might only mean their flavor is substandard, but in a worst-case scenario they might contain heavy metals or cause paralytic shellfish poisoning. Check with local authorities before you harvest from the wild. If you're not up for finding your own, your local fishmonger likely has wild or cultivated mussels in abundance. They're best if eaten immediately, but you can keep them alive in your refrigerator for a few days if they're loosely wrapped in wet newspaper.

Keeping It Simple

• When you're ready to cook the mussels, scrub them briefly under cold running water and cut or pull the stringy "beard" from the hinge side of the shell. Any that don't close tightly when they're being handled are probably dead, and should be discarded for food safety reasons. Like other shellfish, mussels have a small quantity of liquid -- their "liquor" -- inside the shell. The simplest way to cook them is just to place them in a pan, cover it, and cook them for 6 or 7 minutes over medium heat. As the first few mussels open they release a small amount of steam, which helps cook the rest. Cook only until the mussels have just opened.

The Classic Version

• The mussels will steam in their own juices, but adding a few other ingredients to the pot makes them more flavorful. The best-known example of this method is the French "moules marinieres." Although the result is spectacular, it's also an easy meal. Simmer some diced onion or shallot with a sprig or two of thyme, a bay leaf and a healthy splash of dry white wine. Add the mussels and cover the pan, steaming them in the aromatic vapors for just 3 or 4 minutes until they're opened, but still plump and tender. Toss in a lump of butter and some chopped parsley, and shake the pan until it's all well mixed. Serve the mussels with the liquid poured over them.

In Soups and Sauces

• It's relatively easy to keep the mussels tender when you're cooking them on their own, but they often come to grief when they're added to soups, sauces or other dishes, such as risotto or paella. Mussels should always be added at the last minute, whether shucked or -- more often -- in the shell, for their visual appeal. In a cioppino or brothy sauce, 3 to 5 minutes is often enough. In paella and other dry dishes that create less steam, they might need as long as 8 to 10 minutes to cook. Once the majority have opened, discard the rest and serve your dish. Waiting for the last few to open increases the risk you'll overcook and toughen the ones that first opened.