A Guide for Buying and Cooking Mussels
Mussels don't have the same cachet as other shellfish, but when steamed in a mixture of white wine, garlic, parsley and butter, they make a fabulous dinner. Wild mussels are full of sand and dirt, and a chore to clean. Farm-raised mussels are significantly cleaner and just as flavorful.
You should buy 1 to 1 1/2 pounds of mussels per person for a main-course serving. The most common type is the black-colored "blue mussel," but green-shelled New Zealand mussels are popular, too.
Mussels are sold live and their shells should be tightly closed, but some may "gape" open slightly. Try pressing the shell shut. If it stays closed, the mussel is still alive and safe to eat, but if it opens again, throw the mussel away.