Heat oil in large, heavy, nonstick skillet. Saute chicken for 2 min. or until lightly browned. Turn and seal the other side for another 2 min.
Remove all but 1 Tbsp of fat and oil. Add onion, carrot, leek, mushrooms, thyme and pepper. Cover and cook over low heat about 5 min.
Add chicken broth and continue cooking until chicken is done and juices run clear, about 8 min. more.