How to Make It
Combine first 8 ingredients in a 6-quart electric slow cooker. Add chicken to stock mixture; submerge in liquid. Cover and cook on LOW 6 to 8 hours. Remove chicken from cooker. When cool enough to handle, remove bones, and shred chicken into large pieces.
Return chicken to slow cooker; stir in tomatillos, cilantro, juice, and salt. Divide soup among 6 bowls; top evenly with radishes, avocado, tortilla strips, and pepper.