1. Place the potatoes into a 4-quart saucepan. Add water to cover. Heat over high heat to a boil. Reduce the heat to low. Cook for 20 minutes or until the potatoes are tender. Drain. Let cool and cut in cubes. Place the potatoes into a large bowl.
2. Stir the broth, vinegar, flour, sugar, celery seed and black pepper in the saucepan. Stir in the onion. Cook and stir over medium-high heat until the mixture boils and thickens. Reduce the heat to low. Cook for 5 minutes or until the onion is tender.
3. Add the parsley and broth mixture to the potatoes and stir to coat. Serve warm.