Preheat the oven to 150 °C. Rub the roast with salt, coarse pepper and garlic and let it marinate for at least 2 hours. Sear the roast on all sides in lard. Pour the beef broth over it and put it in the oven.
The roast remains in the oven for about 3 hours. Halfway through the roast, turn it over. In between, pour the soup over the roast again and again. 15 minutes before the end of the cooking time, increase the temperature to 200 °C to let the roast take enough color.
Wrap the roast in foil and let it rest for 15 minutes. In the meantime, drain the gravy, season with salt, pepper and mustard and boil down some sauce thickener to the desired consistency. Serve the roast pork together with the sauce.