1. Place a pan of salted water onto a high heat. Bring to the boil.
2. Remove any beards from the mussels (the light-brown hairy stuff). Put the mussels into a large bowl of water and rinse thoroughly. Remove them from the water either with your hands or a spider so that any seaweed/grit remains in the bowl. If the remaining water is particularly dirty then repeat the process. Transfer the drained mussels to a dry bowl.
3. Cut the potato into small cubes (about 2cm). Place a large frying pan onto a medium heat and, when hot, add half the extra-virgin olive oil followed by the potato cubes, a good pinch of salt and pepper, the chilli flakes and crushed garlic clove. Cook gently for 4-5 mins (or until they start to become tender but still retain some bite).
4. While the potatoes cook, add your pasta to the pan of boiling water and set a timer for two mins less than the packet suggests for al dente.
5. Turn up the heat on the frying pan. To the bowl of mussels, add the wine and a couple of parsley stalks. Now carefully tip the mussel-bowl over the potatoes. Shake the pan gently and cover with a lid. Cook for two mins (or until the mussels open up) and then switch off the heat.
NOTE: there may be a few mussels that never open up. C’est la vie. Chuck in the bin.
6. Allow the mussels to cool for a moment before removing from the pan. Pick the meat from the mussels, discard the shells, then add the meat back to the potato mixture. You can leave a few shells for presentation if you like. Pick out, and discard, the garlic clove and parsley stalks.
7. Just before the timer goes off, put the frying pan back on a high heat. Transfer the pasta directly from the pasta-cooking water to the mussel and potato mixture (or scoop out a mug of the water and drain the pasta using a colander). Add in the samphire and toss everything through, adding any pasta-cooking water as needed to create a liquid-sauce consistency.
8. When happy with the consistency, add in the lemon juice and zest, chopped parsley, and remaining half of the olive oil. Toss together until the olive oil has emulsified. Split between warmed plates and slurp away.