Wash the fish fillets, dry with paper towels and remove the bones. Put them in a pot with the white wine, after cutting them into coarse pieces. Add the butter.
Boil the potatoes in salted water, cut the lemon into pieces and then add it to the fish. Season with the spices, cover and let it stew for 15 minutes.
Serve the fish fillets with the boiled potatoes, sprinkle with parsley and gently top with the wine sauce.