Pull the meat off the roasted chicken, eat the crispy skin and put the carcass and bones into a saucepan. Set the meat aside and just barely cover the carcass with water. Peel the onion and add the outer layers of skin to the pan. Bring to a simmer and cook for about half an hour. Strain into a bowl or pot and set aside. You should have 4-6 cups of stock.
Meanwhile, chop the onion and sauté it in a drizzle of oil in a large soup pot set over medium-high heat. Add the carrots, celery, jalapeño, garlic and ginger and cook for a few minutes, until soft. Add the curry paste, cumin and chickpeas and cook for another minute or two.
Add the chicken stock, salt and chopped chicken and bring to a simmer. Cook for about ten minutes, then add the coconut milk and apple and heat through.
Put a scoop of rice into each bowl and ladle the soup overtop. If you like, sprinkle with cilantro and/or chopped peanuts.