1. In a 5-quart flameproof casserole, combine the chicken, onion, chicken stock and water. Bring to a boil over high heat, meanwhile removing all the scum from the surface as it forms.
2. Reduce the heat to low, cover the casserole, and cook undisturbed for 30 minutes, or until the chicken is tender but not falling apart. Transfer the chicken to a plate to cool.
3. Strain the stock through a fine sieve into a bowl, and discard the onion. Skim off and discard as much of the surface fat as you can and return the stock to the casserole.
4. Add the tomatoes, carrots, rice and a few grindings of black pepper, and bring to a boil over high heat. Reduce the heat to low, cover the casserole and simmer, stirring occasionally, for 30 minutes, or until the rice is tender.
5. Remove the skin from the chicken with a small, sharp knife or your fingers. Cut or pull the meat away from the bones. Discard the bones and cut the chicken meat into strips about 1/8 inch wide and 1 to 1˝ inches long.
6. Add the chicken and ham to the simmering soup, and cook for 4 or 5 minutes to heat them through. Stir in the parsley, taste for seasoning, and serve at once, directly from the casserole or from a large tureen.
