Place potatoes in saucepan. Cover with water. Heat to a boil. Cook over low heat 20 minutes or until potatoes are tender. Drain. Cool and cut into cubes.
Mix broth, vinegar, flour, sugar, celery seed, salt and black pepper in saucepan. Add onion. Cook until mixture boils and thickens, stirring constantly. Cook over low heat 5 minutes or until onion is tender.
Toss potatoes, parsley and broth mixture until evenly coated. Serve warm.