Wash the potatoes and cook in boiling water for 20-25 minutes. Peel, wash and slice the carrots. Cook in boiling salted water for about 10 minutes, drain. Wash the meat, dab dry and cut into thin slices (approx. 0.5 cm).
Heat the oil in a frying pan very strongly, fry the meat briefly on each side. Season with salt and pepper. Melt the fat in a pot, sprinkle flour over it and sauté. Deglaze with milk and stock, simmer for about 5 minutes.
Wash the marjoram, dab dry and cut into strips, except for a little to garnish. Stir into the béchamel. Drain the potatoes, quench, peel and slice. Layer the potatoes, carrots and meat in flakes in a gratin dish.
Pour béchamel sauce over it. Grate the cheese and sprinkle over it. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 15 minutes. Garnish with the rest of the marjoram. Serve with fresh salad.