• 600 g small potatoes
• salt and freshly ground black pepper
• 800 g broad beans in the pod, podded (to give you at least 300 g podded beans)
• 1.5 kg greenshell (green-lipped) mussels in the full shell (or 1 kg frozen in the half-shell, defrosted)
• 2 tablespoons extra-virgin olive oil
• 2 medium red onions, thinly sliced
• 2 garlic cloves, thinly sliced
• 2 tablespoons dried hijiki seaweed, soaked in ½ cup of water for 10 minutes
• 125 ml dry white wine or vegetable stock
• 2 handfuls of watercress, roughly cut into 3 cm lengths
• 3 spring onions, sliced into 1 cm lengths
• 1 large juicy lemon, cut into wedges

For the Saffron Cumin Dressing

• 3 tablespoons extra-virgin olive oil
• 1 teaspoon cumin seeds
• 2 good pinches of saffron, soaked in 1 teaspoon warm water

Boil the potatoes in salted water until just tender, then drain – don’t refresh – and, when cool enough to handle, cut in half lengthways. Cook the broad beans in boiling salted water for about 4–6 minutes until just tender, then drain and refresh in cold water. Drain again and squeeze the green beans out of their grey skins.

While the vegetables are cooking, if your mussels are in the whole shell, rinse them thoroughly in plenty of running water, and use a blunt knife to remove any beards and barnacles that are clinging to them. Discard any that have broken shells and that stay open when tapped.

Put a large pot (which has a tight-fitting lid) over a high heat and, when it’s smoking, add the olive oil, then add the onions and garlic, and sauté to colour the onions lightly. Add the drained hijiki and mussels, and give them a good stir in the pot. Add the wine and put on the lid. Cook for 3 minutes, shaking the pot twice. Take the lid off and remove any mussels that have opened and transfer to a bowl, then continue to cook until the rest open – removing them as they do. Any that haven’t opened after 5 minutes should be discarded.

When the mussels are cool enough to handle, remove three-quarters of them from their shells and add the shelled mussels back to the ones in their shells. Cover the bowl with a tea towel or cling film to keep them warm for a few minutes while you assemble the dish.

Make the saffron cumin dressing, place the olive oil in a small pan over moderate heat, add the cumin seeds and cook until they turn golden, then take off the heat and add the saffron and its soaking liquid with 2 tablespoons of the mussel cooking liquor.