Inspect mussels to make sure they are tightly closed. Just before cooking, clean wild mussels by scrubbing with a stiff brush and pulling off the beard with a quick tug. Cultivated mussels need only be rinsed in cold water. To remove meat, either steam open or pry shells open and pick out meat.
Place 1/4-inch (0.635cm) water (wine and seasoning optional) in the bottom of a large pan, and add mussels. Bring water to a boil, reduce heat, and simmer until shells open (four to five minutes). Throw away mussels that don't open. Serve mussels in bowls with broth.
Heat frying pan, then add butter or oil. Add mussel meat and saute until brown, about two to three minutes.