1. In a bowl, wash the mussels thoroughly under cold running water, removing any barnacles and beards that are still present. Discard any mussels that float, including those that are closed. Meanwhile, boil the wine in a small pan for 30 seconds.
2. To cook the mussels, set a large saucepan over a high heat, melt the butter, add the onion and chilli, then stir. Add the wine after about 10 seconds. Bring to the boil, add the mussels and cover with a tight-fitting lid, cooking for 2-3 minutes until the mussels open, then stir in the cream and chopped parsley.
3. To serve the mussels, tip into a large dish or divide among warmed soup bowls.