1. Wash the mussels under plenty of cold running water. Discard any that are open and won't close up when lightly squeezed. Pull out the tough fibrous beards or 'byssus' protruding from between the tightly closed shells. 

2. Knock off any barnacles with a large knife and give the mussels another quick rinse to remove any little bits of shell. 

3. Put the mussels into a very large pan with liquid as given in the recipe. Never more than half-fill the pan. If the pan is overcrowded, those at the bottom will overcook before the heat can reach those at the top. 

4. Cover and cook the mussels over a high heat, shaking the pan vigorously every now and then, for 3-4 minutes until they have all just opened. 

5. Immediately remove the pan from the heat and spoon the mussels into deep bowls