Peel, wash and slice the potatoes. Fry in 2 tablespoons of hot oil, turning for about 12 minutes. Season with salt and pepper. Fry the fish fingers unfrozen in the remaining hot oil at medium heat for 5-8 minutes. Cut cucumbers into slices.
Heat fat for the sauce. Sauté the flour in it. Deglaze with stock and cream. Bring to the boil while stirring constantly. Season with salt, pepper, mustard and cucumber water. Wash the dill and pluck the flags. Add potatoes and cucumber to the fish fingers. Pour the sauce over them. Sprinkle dill over it.
Season with salt, pepper, mustard and cucumber water. Wash the dill and pluck the flags. Add potatoes and cucumber to the fish fingers. Pour the sauce over them. Sprinkle dill over it. Serve garnished with tomato slices and parsley