In a 5-qt. Dutch oven or kettle, combine broth, celery, carrots, bay leaf and parsley; bring to a boil. For dumplings, combine biscuit mix, thyme and nutmeg; stir in milk and parsley just until moistened. Drop by tablespoonfuls onto the boiling broth. Cook, uncovered, for 10 minutes; cover and cook 10 minutes longer. With a slotted spoon, remove dumplings to a serving dish; keep warm. Bring broth to a boil. Reduce heat; add chicken and heat through. Remove bay leaf. Spoon over dumplings.