Place the first 8 ingredients into a 4-quart slow cooker, and stir to combine. Add the chicken and stir gently.
Cover and cook on LOW for 5 hours, stirring once or twice during the cooking.
Turn the cooker to HIGH, and with a slotted spoon, remove the chicken and beans to a mixing bowl, leaving excess liquid in the cooker to reduce slightly.
Use two forks to shred the chicken, then return the chicken and beans to the slow cooker.
Cook uncovered on HIGH for 15 minutes, then turn the cooker off.
Remove the chicken and bean mixture to a serving bowl.
Serve hot, in tacos or burritos (topped with any or all of the optional toppings), or over rice.
Notes
To freeze for later use, remove chicken and beans from the slow cooker and pack into freezer-safe containers. Allow to cool completely before refrigerating or freezing.