In a Dutch oven heat the oil. Add the onion; cook and stir over medium heat, stirring occasionally, until the onion softens (4 to 5 minutes). Add the cumin and garlic; continue cooking, stirring constantly, for 1 minute or until fragrant. Add the remaining ingredients with the exception of the chicken and the sour cream. Over high heat, bring the chili to a boil (4 to 5 minutes); cover, reduce the heat to medium-low. Continue cooking, stirring occasionally, for 15 to 18 minutes or until the rice is tender. Stir in the chicken; heat through (2 to 3 minutes). Top each bowl with a dollop of sour cream. Add a sprinkle of shredded cheese and a sprinkle of cilantro, if desired. Refrigerate leftovers.