Soak the raisins in the brandy and the bread crumbs in the milk.
Heat the oil in a large frypan and fry the onion for a few minutes. Add apple and fry 5 more minutes. Add diced chestnuts and fry 5 more minutes. Add mushrooms, stir and let cool.
Drain the raisins, reserving the brandy. Drain the bread crumbs and squeeze out the milk. In a bowl, combine the onion mixture, drained bread crumbs, ground almonds, egg, 1 tablespoon of the brandy and season with salt and pepper.
Preheat the oven to 180 degrees C. Salt the chicken inside and out and stuff. Tie closed or seal with poultry clips. Place in a roasting tin with the onion and carrots. Cover with aluminium foil and bake 1 hour, basting occasionally.
After 1 hour, remove the foil and cook 30 minutes more, basting every 15 minutes. Add the 500g chestnuts and cook 30 more minutes, for 2 hours in total. Let rest 30 minutes before serving.