Soak the clams in cold water while you prepare the other ingredients (ideally soak for 20 minutes if you can).
Finley dice the onion and garlic and roughly chop the parsley.
Remove the skin from the sausage.
Set a pot of salted water to boil for the pasta.
Drain the clams and rinse and scrub off any remaining grit and dirt.
Warm the oil in a wide pan and add the onion. Once it has softened slightly, add the garlic, stir and cook a minute, then add the sausage. Break the sausage up as it cooks.
Once the sausage has gently browned, deglaze pan with the wine (i.e. add the wine and scrape any browning from the pathen add the clams in a layer. Cover the pan and allow to steam.
Meanwhile, add the pasta to the pan of water and cook until al dente. Drain and cover to keep warm.
Discard any clams that don't open, then mix the pasta in with the sauce (you may find it easiest to take the clams out then mix the pasta with the rest).
Transfer to bowls, with clams served on top, and sprinkle with the parsley.