Mussels are Clear shells scraped, hairs are removed and put in a saucepan. Watered with the wine, add the chopped onion and cook on medium heat until open. Drain and leave to cool. Separate the interior, while retaining the half-shell in each clamshell. Flour, milk and egg yolk make dough. Add salt and pepper, and stir until a homogeneous mixture, and then adding the egg white. Stir again carefully. All clams are dipped one by one and put each in a shell. Fry in oil bath, first with shells down while overlaid and then turns. Mussels drain on kitchen paper and serve.