Heat the oil in a large heavy pan and gently soften the onion and garlic.

Add the chopped tomatoes with their juice, season with salt and pepper to taste, and let the sauce simmer for about 15 minutes until soft arid smooth.

Meanwhile, in another large pan, steam open the clams or cockles in a little water. When they have all opened, reserve 12 intact to use as a garnish, then remove the rest from their shells.

Pour all the cooking liquor into the simmering tomato sauce. Continue to simmer the sauce over a low heat as it reduces a little and thickens.

Now cook the pasta in plenty of boiling salted water to which you have added a drop of olive oil to prevent it sticking.

Fresh pasta takes no more than 2 minutes to cook al dente (firm to the bite), dried takes longer follow the directions on the packet.

Drain the pasta thoroughly and put it into a large shallow serving dish. Keep it warm while you add the shelled cockles or clams to the reduced sauce and gently heat through.

Pour the sauce over the pasta and fork it well in.

Scatter the reserved clams or cockles in their shells over the dish, sprinkle with the chopped parsley and serve immediately.