Wash and scrape the mussels.
Cook the mussels in a shallow pan in the white wine until they open. Save the juice.
Retain those halves of the shells containing the mussels. Lay them on a grilling tray.
In another pan melt the butter, add the onions and cook for 2 or 3 minutes until soft. Add the parsley, the juice from the mussels, the cream and the cheese. Bubble for a m