Heat some olive oil in a skillet and sauté the chopped onion until softened, about 3 minutes. Deglaze the pan with the brandy, allowing the alcohol to evaporate and the mixture to dry out, concentrating the flavors.

Add the rice, chopped chestnuts, pine nuts, raisins, and broth to the skillet. Allow the filling to absorb almost all the liquid, then season with salt and pepper.

Coat the chicken with mustard and sprinkle with coarsely ground mustard seeds if using. Fill the cavity of the chicken with half of the prepared filling, seasoning it beforehand, and then sew the opening shut. Tie the legs of the chicken securely, brush it with a little oil, and season with salt and pepper. Place the chicken in a Dutch oven (or roasting pan).

Clean the apples and hollow them out. Fill them with the remaining stuffing. Alternatively, you can cut the apples in half and stuff them like you would with eggplants. Arrange the stuffed apples alongside the chicken in the pot. Drizzle with olive oil and orange juice, and add the prunes along with a little water.

Cover the Dutch oven and roast in a preheated oven at 180°C (350°F) for 1 hour and 10 minutes. Then, check if there is enough liquid in the pot. If it looks low, add a bit of water or broth. Continue roasting for another 30 minutes without the lid, until the chicken is golden brown.

To ensure the chicken is cooked through, insert a knife into the thigh; if the juices run clear, it’s done. The sauce that remains will be delicious, as the prunes will almost melt alongside the apples, combining with the chicken juices.