In a large bowl, combine the egg, 1/4 cup onion and bread crumbs. Crumble turkey over mixture and mix well. Shape into 1-in. balls. In a large skillet, brown meatballs in oil until no longer pink; drain and set aside. , Meanwhile, in a large saucepan, saute the carrots, celery and remaining onion in butter until crisp-tender. Add the spinach, broth, chicken, parsley, thyme, salt, pepper and reserved meatballs. Cook, uncovered, over medium heat for 10 minutes. , Bring to a boil. Add pasta; cook, uncovered, for 6-7 minutes or until pasta is tender, stirring occasionally.