When I had my first restaurant on Tower Bridge Road, I became friends with some wealthy Parisians whose parents had an old farmhouse in Normandy, complete with a cider press and a still for making Calvados.
I remember eating this dish with them there, and years later I put it on the menu at The Tree Bistro. Classically, Moules Marinière doesn’t contain crème fraîche, but my customers loved the addition — so it stayed.