Heat oil in a large Dutch oven over medium-high heat. Add onion; saute 5 minutes. Add chili powder and next 4 ingredients (powder through garlic); saute 30 seconds. Add Chicken Stock, beans, and tomatoes; bring to a boil. Reduce heat to medium-low; simmer 30 minutes. Stir in chicken; simmer 15 minutes. Serve with cheese and sour cream.