Discard husks and stems from the tomatillos, and finely chop. Combine tomatillos and the next 6 ingredients (through pepper) in a medium bowl.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Sprinkle chicken evenly with seasoning. Add chicken to pan; cook 3 minutes. Turn chicken over. Reduce heat, and cook 5 minutes or until done. Serve chicken with tomatillo mixture.