Bring a pot of salted water to a boil and cook pasta according to the package instructions.
Over medium heat, fry onion in a little olive oil until soft.
Add garlic, parsley and chilli and fry for another minute, then add the wine.
Let wine reduce to about half, then add the butter and season with salt and black pepper. Once butter has melted add half a cup of the pasta water to the sauce and simmer for a couple of minutes, then add the snails.
About 2 minutes before the pasta is done cooking, transfer it to the sauce (discarding the water) and finish cooking in the sauce.
For the drizzling oil
Make sure the chilli, garlic and parsley are all finely chopped, then add the olive oil and balsamic vinegar and combine well.
Drizzle over pasta just before serving.
To serve:
Add a generous amount of parmesan cheese and fresh parsley.