Heat vegetable oil in a heavy skillet over medium-high heat. Cook and stir chicken until browned and no longer pink in the center, about 8 minutes per side. Transfer chicken to a slow cooker, draining any excess oil. Add tomatoes, chicken stock, kidney beans, onion, jalapeno pepper, and chili powder to slow cooker.
Cook on Low for 6 to 8 hours or on High for 4 hours.
It's important to use the roasted tomatoes, otherwise you won't get the same robust flavor. You may substitute chicken thighs for chicken breasts, but the thighs add to the flavor as well. These work together to give you that bold flavor so you won't miss the beef in this recipe. It's not necessary to use the slow cooker. You can simmer this same recipe in the skillet for 30-45 minutes so you can enjoy it in a jiff!