Make a diamond-shaped incision in the rind and soak the rind for 2 hours.
Pat the meat dry and season with salt and pepper. In an ovenproof roaster, brown in oil on all sides except on the rind and remove the meat from the roaster.
Sauté the half onion rings in the meat fat until lightly golden. Place the meat on top with the rind facing upwards.
Put it in the oven preheated to 200 °C and add some Pilsner. Do not pour the Pils over the meat for the first half hour, otherwise the roast will not be crispy.
The roast must stay in the oven for about 2.5 hours. After half an hour reduce the temperature to 180 °C. Keep pouring Pilsner (500 ml in total) over the meat, otherwise it will become dry.
After the cooking time, remove the meat from the roaster and let it rest a bit. Puree the sauce with a blender and if it is too thick, extend it with a little water.
Season the sauce with salt, pepper and possibly a little nutmeg.