Sopa de Pollo a la Mexicana (Mexican Chicken Soup) Recipe

In Dutch oven, combine chicken, water, onion slices, celery, salt and pepper. Simmer, covered for 2 hours or till chicken is tender. Remove chicken from broth. Strain broth, discarding vegetables; return broth to Dutch oven. Add undrained tomatoes, carrots, onion and bouillon granules; simmer, cover for 30 minutes or until the carrots are tender. Meanwhile, when chicken is cool enough to handle, remove and discard skin and bones. Cube chicken and add to broth along with zucchini and peas. Cover and simmer 10 to 15 minutes longer or until vegetables are tender. Just before serving, garnish with avocado slices.