Cut fish fillet with skin into portion pieces, place in a greased frying pan, season with salt, season with pepper.
Place slices of half-cooked potatoes around the fish, pour steamed sauce over them, sprinkle with grated cheese, pour melted butter over them and bake in preheated oven until a reddish crust appears.
Before serving, baste with melted butter and sprinkle with chopped parsley.