In a medium nonstick skillet, heat the oil over medium heat. Add the onion and garlic, then cook until soft, about 3 minutes. Scoop into the slow cook along with the rest of the soup ingredients. Cover and cook on low for 4 to 6 hours.
Remove the chicken and shred with 2 forks. Then return the chicken to the slow cooker.
For the Toppings:
To serve, ladle the soup into 6 bowls, then divide the toppings evenly among them.
This recipe is paraphrased from The Skinnytaste Cookbook. Read chicken broth label to make sure it's gluten free.