Clean the mussels, removing any beards and barnacles. Rinse thoroughly.
Wash the new potatoes and cut in half or into quarters. Place in a pan with cold salted water. Bring to the boil and cook until tender. Once cooked, drain and set aside.
Peel and finely dice the onion. Wash the parsley and pick the leaves from the stalks. Reserve the stalks and finely chop the leaves.
Heat a large pan and then sweat the onions with half of the butter and a pinch of salt. Once the onions start to soften, add the parsley stalks, the whole garlic clove and the bay leaf. Add the beer to the pan and bring to the boil. Reduce to a simmer, add the mussels and cover. Stir and then add the chopped parsley. Cover and cook for a further 2 minutes. Stop cooking as soon as the mussels are open.
Whilst the mussels are cooking, melt the rest of the butter and then pan-fry the potatoes until golden brown.
Serve the mussels with the sautéed potatoes.
«Do not overcook your mussels: once they are open, they are ready to eat. Discard any mussels that do not open.»