Preheat the oven grill (broiler). Carefully wash the mussels in cold water, discarding any that are open. Scrub the shells and remove the beards with an up and down motion to pry them loose. Keep the cleaned mussels in a damp cloth in the refrigerator if you are preparing them a few hours ahead of time.
Put the mussels into a saucepan, cover and put over a high heat for a couple of minu