Wash the fish, dab dry. Cut bacon into fine strips. Peel and coarsely grate potatoes. Sprinkle fish with lemon juice, then season with salt and pepper, sprinkle with bacon strips and potato shavings. Wash parsley, cut into fine strips and sprinkle over the fish. Cut butter into thin slices and place on the fish fillet. Cook in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 15-20 minutes