Prepare a ceramic (not metal) casserole dish and heat-resistant microwave foil (safe to 160°C / 320°F).
Butter the inside of the ceramic dish. Generously rub the duck inside and out with salt and pepper. If the duck contains innards, remove and place in the dish except for the liver (which set aside).
Preheat the oven to 120°C / 250°F with top and bottom heat. Squeeze 3 of the 5 oranges and the organic lemon; pour the juice into the dish. Add the zest from the organic orange and organic lemon to the dish. Pour 2-3 tablespoons of this juice into the duck's cavity. Place the onion studded with 3 cloves and the grated organic orange (without white pith) into the duck cavity along with half the sliced ginger.
Seal the duck's belly opening with skewers or roulade needles. Stir the orange jam and remaining ginger into the remaining juice in the dish. Place the duck in the dish. Cover tightly with microwave foil, pressing edges firmly to seal (lightly moisten edges beforehand for better adhesion).
Bake for 4 hours 30 minutes at 120°C / 250°F with top and bottom heat.
Remove the dish from the oven and carefully pull away the foil. Change the oven setting to grill function at 220°C / 425°F and let it preheat.
While the oven preheats, skim the duck fat from the braising liquid (you should collect roughly 400-500 ml). Transfer the fat to a glass container.
Pat the liver dry with paper towels. Place on aluminum foil, drizzle with 1 tablespoon of the reserved duck fat, season with salt and pepper, and place in the oven next to the duck to grill.
Grill the duck and liver until the duck skin is crispy; watch both to prevent burning.
Remove the duck and liver from the oven. Transfer the duck to a serving platter and decorate with the remaining 2 oranges (peeled, sliced, white pith removed). Turn off the oven but leave the door open to keep the duck warm.
Strain the braising liquid through a fine sieve and skim off any additional fat. Drizzle some of the sauce over the orange slices and serve the remainder on the side.
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