Drain the mussels. Peel and finely chop the onions and garlic. Heat the oil in a pan, fry the onions and garlic, add the mussel meat and fry briefly. Deglaze with wine and season with salt and pepper.
Wash the parsley and, except for something to garnish, chop finely and stir in. Divide the mussels into four ovenproof dishes, add double cream, sprinkle with coarse pepper and bake under a preheated grill.
Garnish with parsley.