Combine in a small bowl paprika, salt, garlic powder, pepper. Sprinkle over chicken; rub in with your fingers.
Place chicken in a 4 1/2 to 5 1/2-quart slow cooker. In a separate bowl, whisk together chicken broth and tomato paste. Pour over chicken in cooker.
Cover and cook on low heat setting for 6 to 7 hours or on high heat setting for 3 to 3 1/2 hours.
Remove chicken to a serving platter, reserving cooking liquid. Cover the chicken with foil to keep warm.
Turn cooker to high heat setting. Combine in a small bowl sour cream and cornstarch. Whisk into liquid in cooker until smooth. Cover and cook for 15 minutes more or until thickened. Spoon sauce over chicken.