Season fish with salt and juice of one lemon. Put in a saucepan and put slices of lemon, add salted water and stew until tender. Reduce wine and vinegar to 1/3. Add whipped cream, stock and spinach, knead flour and butter in it. To serve, place the fish on the pale green sauce and brush with a tiny bit of liquid butter until glossy.
Our tip: Use the young, tender spinach from the farmer’s market!