In a 2-quart Dutch oven or heavy pot, heat oil over medium heat. Brown half the chicken and set aside. Repeat with remaining chicken and set aside.
4
Add onions and garlic to the pot and cook until onions are tender. Return chicken to the pot. Add all ingredients except the mango to the pot. Cover and simmer for at least 20 minutes. Add small amount of additional liquid if too thick.
5
While the chili simmers, peel, seed, and chop mango. Reserve about a 1/4 cup of the chopped mango and add the rest to the pot. Heat through, about 5 minutes.
6
Serve chili in bowls with optional dollop of sour cream topped with reserved mango.