Heat the olive oil in a large pot or Dutch oven over medium heat. Add the diced onion and sauté for about 5 minutes, until softened.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the chicken pieces to the pot, and cook for about 5-7 minutes, stirring occasionally, until the chicken is no longer pink.
Sprinkle in the ground cumin, chili powder, smoked paprika, and cayenne pepper (if using). Stir to coat the chicken evenly with the spices.
Pour in the diced tomatoes (with juices), kidney beans, black beans, and chicken broth. Mix everything together well.
Bring the mixture to a boil, then reduce the heat to low and let it simmer uncovered for about 30 minutes, stirring occasionally.
Season with salt and pepper to taste. If you prefer a thicker chili, let it simmer for an additional 5-10 minutes.
Serve hot, garnished with fresh cilantro, sour cream, and shredded cheese if desired.