Spray a 6-quart slow cooker with nonstick spray. Trim excess fat from the chicken and cut it into 2-inch chunks. Rinse the quinoa in a fine-mesh sieve and set it aside.
If your slow cooker has a sauté function, use that; otherwise, heat olive oil in a pot over medium-high heat. Add the onion and sauté until golden, about 5–7 minutes. Then, add garlic and sauté until fragrant, about 30 seconds. Stir in the tomato paste, seasoning blend, salt, and pepper. Sauté for another 1–2 minutes until fragrant.
Pour in diced tomatoes without draining, mixing well and scraping any browned bits from the bottom of the pan. Transfer this mixture into the slow cooker.
Add chili beans, corn, black beans, chicken thighs, quinoa, and chicken stock to the Crock-Pot. Stir thoroughly, ensuring the chicken is submerged in the liquid. Cook on high for 3–4 hours, or until chicken shreds easily (see note 5).
Once cooked, remove the chicken and place it in a bowl. Shred the chicken using two forks, then return it to the slow cooker. For a heartier texture, you can also mash some of the squash.
Add in the cilantro and lime juice if using. Taste and adjust seasonings, adding more salt or pepper if desired. Ladle into bowls and add desired toppings. Enjoy immediately!
