To a 6-quart slow cooker, add all of the ingredients except for the toppings. Stir to combine.
Cover and cook on LOW for 8 hours or on HIGH for 4 hours.
Remove the chicken from the slow cooker and transfer to a plate or cutting board. Use two forks to shred the chicken. Remove the bay leaf from the soup.
Return the chicken to the slow cooker and stir to combine.
Portion the soup into bowls. Add avocado, jalapeno, shredded cheese, and sour cream for garnish, if desired. Serve warm.
Notes
Nutritional information does not include optional toppings.