In a large skillet, heat oil over medium heat. Add peppers and onion; cook and stir until tender, 6-8 minutes. Add garlic; cook 1 minute longer. Transfer pepper mixture and chicken to a 5- or 6-qt. slow cooker. Stir in broth, tomatoes, enchilada sauce, tomato paste, seasonings and, if desired, pepper sauce. Cook, covered, on low 6-8 hours or until chicken is tender (a thermometer should read at least 165°)., Remove chicken from slow cooker. Shred with 2 forks; return to slow cooker. Stir in cilantro. Serve with toppings as desired. Freeze option: Freeze cooled soup in freezer containers. To use, partially thaw in refrigerator overnight. Heat through in a saucepan, stirring occasionally; add a little water if necessary.