Debeard and scrub mussels. Discard any that don’t shut when tapped.
In a saucepan large enough to hold the mussels comfortably and which has a lid, sweat the leek in the butter until just soft. Pour over the wine or cider, bring to the boil, lower the heat and simmer for 5 minutes.
Turn up the heat and sprinkle the contents of the pan with pepper. Add the mussels, cover with the