Peel and finely chop the onion. Mix tartar, corn, egg and onion. Season to taste with salt and pepper. Form 2 meatballs from it. Fry in hot oil while turning for about 10 minutes. In the meantime clean and wash the leek and cut into thin rings.
Cook in boiling broth for about 8 minutes. Sprinkle in sauce thickener. Refine with sour cream. Season to taste with salt and pepper. Boiled potatoes taste good with it. Serve sprinkled with parsley and garnished.