Clean, wash and cut the leek into rings. Cut bread first into slices, then into cubes. Grate cheese roughly. Peel garlic and chop finely.
Melt the butter in a large ovenproof pan. Roast the bread cubes in it while turning and take them out. Heat the oil in the pan. Steam leek and garlic for about 5 minutes. Season with salt and pepper.
Take out half of the leek. Spread half the bread and half the roast beef on the leek in the pan. Pluck the roast beef smaller if necessary. Sprinkle with half the cheese. Add the rest of the leek, bread and roast beef in the same way.
Sprinkle with the remaining cheese and bake in a preheated oven (electric oven: 225 °C/circulating air: 200 °C/gas: level 4) for approx. 10 minutes. Wash the chives, dab dry, cut into small rolls with kitchen scissors and sprinkle over.
Drink tip: red wine, e.g. a smooth Merlot.