In a large skillet, heat oil over medium heat. Add peppers and onion; cook and stir 6-8 minutes or until tender. 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. Return to slow cooker. Stir in cilantro. Serve with toppings as desired.
Notes
Store Leftovers in the refrigerator in an airtight container for up to 4 days. Freeze cooled soup in freezer containers for up to 3 months. Make on the stovetop: Follow all of the instructions for slow cooker method, preparing on the stovetop in a dutch oven. Start to finish the soup took about 45 minutes.Adapted from Taste of Home Simple and Delicious Cookbook