Step 1: If searing chicken (optional, but recommended for deeper flavor), heat 1 tablespoon olive oil in a large skillet over medium-high heat. Sear chicken thighs for 2-3 minutes per side until lightly browned. Transfer seared chicken to the bottom of a 6-quart or larger slow cooker. If not searing, place raw chicken directly in the slow cooker.
Step 2: Add the diced onion, minced garlic, cubed sweet potatoes, and diced red bell pepper over the chicken in the slow cooker.
Step 3: Pour in the crushed tomatoes and chicken broth. Add the rinsed and drained black beans and kidney beans.
Step 4: Sprinkle in the chili powder, ground cumin, smoked paprika, dried oregano, and cayenne pepper (if using). Season generously with salt and black pepper.
Step 5: Stir everything gently to combine, ensuring the chicken is mostly submerged in the liquid.
Step 6: Cover the slow cooker and cook on LOW for 6-8 hours or on HIGH for 3-4 hours, or until the chicken is very tender and the sweet potatoes are soft.
Step 7: Carefully remove the cooked chicken thighs from the slow cooker. Using two forks, shred the chicken and then return it to the slow cooker. Stir to combine with the chili.
Step 8: Taste the slow cooker chicken and sweet potato chili and adjust seasonings as needed. You may want to add more salt, pepper, or a squeeze of lime juice to brighten the flavors.
Step 9: Ladle the hot chili into bowls and serve with your favorite toppings such as fresh cilantro, shredded cheese, a dollop of sour cream or Greek yogurt, and diced avocado. Enjoy your delicious slow cooker chicken and sweet potato chili!