Separate the mussels from the shell and chop them. Set aside.
Cut the onion into brunoise and fry in a pan with a drizzle of oil.
Add flour, cooking cream and stir. Add more or less cream as needed.
Add the mussels with a pinch of salt, set aside and cool. Fill the mussel shells with the mixture.
Dredge them in flour, egg and breadcrumbs.
In abundant oil, fry them until golden brown and, let's eat!