Wash the fillet and dab dry. Sauté in hot oil while turning. Season with salt and pepper. Fry for about 8 minutes at medium heat until done. Meanwhile clean and wash the leek and cut into fine rings.
Peel, wash and roughly grate the carrots. Bring the stock to the boil briefly. Cook leek and carrots for about 3 minutes. Stir in cheese and melt in it. Season to taste with salt and pepper. Cut fillet into slices.
Spread the prepared ingredients over 4 slices of bread. Bake in a preheated oven (electric: 200 °C/ gas: level 3) for 6-8 minutes. Serve garnished with fresh parsley.