1. Heat a large saucepan over medium-high heat. Coat pan with cooking spray. Add chicken to pan; cook 4 minutes, browning on all sides. Remove chicken from pan; keep warm. Add celery and next 5 ingredients (through bay leaf) to pan; sauté 5 minutes or until onion is tender. Return chicken to pan; cook 1 minute. Add broth to pan; bring mixture to a boil. Cover, reduce heat, and simmer 30 minutes.
2. Weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, chopped parsley, baking powder, and salt in a medium bowl. Add milk, stirring just until moist. Spoon by heaping teaspoonfuls into broth mixture; cover and simmer 10 minutes or until dumplings are done. Discard parsley sprigs and bay leaf.