Mix all the marinade ingredients. Place the roast in the marinade and refrigerate for 24 hours. Turn the meat over after 12 hours. Once the marinating is done, remove the mirepoix using a colander and discard the beer. Put the mirepoix in a roasting pan.
Take the roast out of the refrigerator 15 minutes before cooking. Pat dry with paper towel before putting it in a frying pan, searing it on all sides. Take the roast out of the pan, coat with Dijon mustard and place the mirepoix in the marinade. Cook in a preheated oven at 375°F (190°C) uncovered, for 45 minutes or until the internal temperature reaches 145°F (63°C). Remove roast from the oven and cover loosely with aluminium foil. Let rest for 10 minutes before slicing. In the meantime, make the sauce.
Once again, remove the mirepoix from the pan using a colander and pour into a pot. Add the duck stock and apple jelly. Let simmer for a few minutes to thicken. Drizzle sauce over the roast and serve.
