Melt the butter in a pan over high heat, add shallots and cook, stirring often, for 2–3 minutes. Add the mussels to the pan and saute for about 2 minutes.
Pour the white wine over and sprinkle with thyme. Cover with the lid and steam through for about 5 minutes on high heat.
While steaming, it’s important to shake the pan regularly.
Once the mussels have been steamed thoroughly, pour the contents of the pan into a deep bowl. Add heavy cream at this point if you wish to make ‘creamed mussels’ rather than ‘mussels marinière’.
Sprinkle over chopped parsley and serve with sliced baguettes or croutons.
The best mussels to use for this recipe are bouchot mussels, which originate from Brittany and are known for their sweetness and smaller size. However, the recipe works well with other varieties as well, especially if you prefer larger mussels.