Prepare a marinade with the juices, beer, oregano, garlic, ginger, cloves, cinnamon, salt, and pepper. Let the meat marinate for 5 hours. Set aside.
Roast the meat in the oven at a high temperature, 400°F (200°C). Halfway through cooking, cover the meat with aluminum foil and lower the temperature to 300°F (150°C). Bake for another hour and a half.
Soak the prunes in some warm water, then blend them. Put the blended prunes in a pot with the wine, sugar, cinnamon, and mustard. Cook for 8 minutes. Remove from the heat and spread the sauce over the meat. Put it back in the oven to brown. Decorate the dish with whole prunes.
