"Learned to cook food from Kerala, south India, from my in-laws. This is a fantastic main dish for a South Indian meal, which should always be served with several dishes - see the footnote for suggestions."
Cut the chicken into big chunks, about 1.5". If you've bought chicken with bones, let the bones cook with the dish - this adds flavor.
Heat the oil in a large frying pan with a lid until it is hot but not smoking. Drop in the mustard seeds and cumin seeds, then cover the pan and wait until the mustard seeds have all popped. Uncover, then add the onions, ginger and curry leaves (optional). Saute for about 5 min. over medium heat. Add the tomatoes, turmeric, coriander, chili powder, and cinnamon stick, and stir well. Add the chicken, and bring to a boil, adding enough water to barely cover the chicken. Cover the pan, and simmer over med or med-low heat for about 45 minutes, checking every 10 minutes or so to make sure there is enough moisture in the dish to keep the chicken from burning - add more water if necessary. When the chicken is tender, add the salt and serve.