Combine ingredients to make a marinade. Marinate chicken, covered, for at least 2 hours in the refrigerator.
Place the potatoes in a pan and cover with water. Boil them for about 15 minutes, then drain.
Heat the oil in a large skillet. Sautee the onions until they are golden-brown, about 10 minutes. Remove the onions and drain.
Add the potatoes to the oil (adding more oil if necessary) and fry them until they are slightly crisp, at least 5 minutes. Remove the potatoes, drain, and reserve them.
Combine the onions, chicken, marinade, and the 1/2 C. water in a large skillet. Cook, covered, over low heat until the chicken is very tender, at least 35 MINUTES. During the last 15 minutes, add the potatoes and cook, stirring occasionally.
Serve garnished with the cilantro leaves.