Clean, wash and cut the leek into pieces of about 8 cm length. Peel the garlic, cut the cloves of one bulb in half. Wash the oregano, put something aside for garnishing, chop the rest. Wash the roast, dab dry and prick with a sharp knife about 1 cm deep several times close together at a distance of about 2 cm. Put halved garlic cloves into the deepenings. Rub the roast with salt and pepper.
Heat butter in a roasting pan, fry leek and the rest of the garlic. Season with salt and pepper. Place the roast on the leek and sprinkle with oregano. Cover and cook in the preheated oven (electric cooker: 200 °C/recirculating air: 175 °/gas: level 3) for about 2 hours (close the lid well!!!). Garnish with oregano put aside. Bread tastes good with it