1–1.5 kg (2–3 lb) large mussels, cleaned (about 48 mussels)
60 g (2 1/4 oz) breadcrumbs
50 g (2 oz) walnut pieces
200 g (7 oz) butter
6 garlic cloves, chopped
juice of 1 lemon
2 tablespoons grated Parmesan cheese
2 tablespoons chopped tarragon
a small handful of parsley, chopped
Steam the mussels in a large, covered saucepan until they open, then drain. Discard any mussels that do not open. Break off the empty half of the shells and place the mussels on a baking tray.
Place the breadcrumbs, walnuts, butter, garlic, lemon juice and grated Parmesan in a food processor and blitz until the mixture starts to come together. Add the herbs and blend until combined.
Divide the herb mixture between the mussels, making sure each mussel is covered. Cook under a preheated hot grill for 2–3 minutes, until the stuffing is golden. You may need to cook the mussels in batches if you cannot fit them all on 1 baking tray.