About three-quarters of mussels on sale today are cultivated. The rest are harvested from the wild. Mussels filter seawater through their bodies to extract nutrients and may pick up any toxins in the water. Whether cultivated or wild, they must be carefully cleaned before being cooked.
Scrape off any barnacles from the outsides of the shells with the back of a small knife.
With your thumb against the blade, pull out and detach any hair-like “beards” from the hinges of the shells.
Scrub each shell briskly under cold running water w’th a stiff brush. This will remove any sand and thoroughly clean the mussels before cooking. Discard any mussels with cracked shells and any that do not close when tapped. Place cleaned mussels in a bowl of lightly salted cold water for about 2 hours or until ready to use.