Use a 6-quart slow cooker. Place chicken thighs into the slow cooker. Remove casings from chorizo and crumble the meat into a large skillet. Brown on the stovetop with onion and garlic until the onion is translucent. Drain any accumulated grease and pour the meat mixture into the slow cooker. Add bell pepper, tomatoes and juice, carrot, parsley, thyme, and frozen corn. Pour in chicken broth and stir well to combine.

Cover and cook on low for 6-8 hours, or on high for 4-5 hours. Gently shred the chicken with a fork into bite-sized pieces before ladling into bowls. Serve with a dollop of sour cream, if desired.