Peel and wash the potatoes, carrots and celery. Clean and wash the leek. Cut celery and leek into fine strips, potatoes into cubes, carrots into rhombic shapes. Blanch potatoes in boiling salted water for 3 minutes, then drain.
Melt the fat. Sauté vegetables in it. Deglaze with vegetable stock. Cover and cook for another 3-5 minutes. In the meantime season the fillet slices with salt and pepper. Clean and wash spring onions and cut into rings.
Bring the meat stock, peppercorns and spring onion rings briefly to the boil. Steam veal fillets in it for about 5 minutes. Wash the chives and cut into small rolls. Drain the vegetables, refine the stock with cream, sprinkle with sauce thickener, bring to the boil briefly.
Season to taste with salt and pepper. Serve the fillets and vegetables garnished with the sauce and parsley.