Note: for a quicker version you can use 2 cups of shredded cooked chicken and 4 cups chicken broth and skip the first step below.Place the chicken in a stock pot with 5 cups water. Add a stalk of celery and a carrot cut into 2-inch pieces. Add a bay leaf and a few black peppercorns. Bring to a boil, reduce the heat to low, cover and simmer for 1 hour. Discard the vegetables and bay leaf. Place the chicken on a plate and discard the skin. Shred the meat with two forks. Set the meat aside. Once the chicken stock has cooled, skim the fat off the surface and discard.
Heat the oil in a Dutch oven over medium-high. Saute the onion until translucent and just beginning to caramelize. Add the garlic and jalapeno and cook for another minute. Add the red bell pepper and cook for 3-4 minutes. Add all remaining ingredients, bring to a boil, reduce the heat to medium, cover and simmer for 25 minutes. Serve with a dollop of sour cream and shredded Cheddar cheese, if desired.Note: this soup tastes even better the next day!