Carefully scrub the mussels. Wash 2 or 3 times under running water, then drain. Keep in the fridge. ciseler the shallots and chop the parsley.

Put the drained mussels in a pot with the white wine.

Add the shallots and parsley.

Add chunks of butter...

...a dash of oil...

...and a bit of vinegar.

Season. Be cautious with the salt as the mussels are naturally salty.

Cook, lid on, for 6 to 8 minutes. Stir from time to time.

Remove from the heat when all the mussels open.

Arrange the mussels in a large bowl, using a skimmer. Add 100 g butter to the broth, stirring to combine it. Pour the juice on the mussels, watching out for the sand that could have stayed with the mussels. Sprinkle with chopped parsley. Serve hot.