First clean the leek and carrots and cut into thin rings and slices. Roughly dice the onion and the clove of garlic.
In a large saucepan, sauté the vegetables in a little olive oil. Add the rosemary and thyme, deglaze with white wine and season with salt.
Clean the mussels and rinse under very cold water. Throw away mussels that do not close.
For the cheese sauce, heat the cream in a separate saucepan, melt the Roquefort in it and reduce it a little.
Put the drained mussels in the boiling white wine stock and cook for about 10 minutes with the lid closed, shaking the pot again and again so that the mussels spread out a little. The mussels, which are not covered by the brew, cook with the steam. The clams are ready when they are fully open. Throw away unopened mussels.
Skim off some of the white wine stock and stir into the cheese sauce. Skim off the mussels and arrange on a plate. Pour the cheese sauce over it.