Cleaned fish fillets cut into cubes with a side of 3 cm, marinated in vinegar, pepper and salt and let stand 30 minutes. Chopped onion stew in the vegetable oil 3-4 minutes. Add sliced ​​boiled potatoes, scatter with salt and pepper, stir and fry for 5-6 minutes. Add cooked fish, stir and fry for 10 minutes. A solution in wine mustard, cover with lid and after 2-3 minutes the dish retired from the fire. Sprinkle with chopped parsley and serve.