Clean the mussels under running water, pulling out all the beards. Discard any with damaged shells or open ones that do not close when tapped. Place them in a pan with the wine, cover and bring to the boil. Cook over a high heat for 2-3 minutes until they have opened. Take the pan off the heat and leave the mussels to cool.
Strain the cooking liquid through a fine sieve into a small bowl and discard any mussels that have not opened. Whisk the lemon juice into the strained mussel liquor to make a dressing. Add salt and pepper to taste and set it aside.
Bring a large pan of water to the boil, add the pasta and a pinch of salt and cook according to the instructions on the packet. Strain and place in a large bowl with a little of the mussel dressing stirred through to prevent it from drying out.
Cut the prawns in half if they are large. Add the mussels, prawns, garlic, parsley and spring onions to the pasta and mix them thoroughly.
Pour the rest of the mussel dressing over the salad and mix well. Cover and chill for a few hours for the flavours to develop, then adjust the seasoning to taste. Bring the salad to room temperature before serving.
Variation: the mussels are essential to this recipe, but you can substitute scallops and/or squid for the prawns.