How to Make It
In a stockpot, combine the chicken and neck with the water, quartered onion, chopped carrots and celery, garlic, peppercorns, bay leaf, parsley springs and thyme sprigs and bring to a boil. Cover partially and simmer over low heat for 30 minutes. Transfer the chicken to a plate. Discard the skin. Pull the meat off the bones, cut it into 1/2-inch pieces and refrigerate.
Return the bones to the pot, partially cover and simmer for 1 hour, until the broth is richly flavored. Strain the broth into a clean heat proof bowl and rinse out the pot. Return the broth to the pot and boil over moderate heat until reduced to 8 cups, about 30 minutes. Season with salt.
In a large saucepan, heat the vegetable oil. Add the sliced onion, ginger, tomatoes, curry powder and tomato paste and cook over moderate heat, stirring, until softened, about 7 minutes. Stir in the broth, coconut milk and banana and bring to a boil. Season with salt and cook over moderate heat until the banana is very tender, about 30 minutes. Add the chopped chicken and cilantro and simmer until just heated through. Ladle into bowls and serve.