1. Cook bacon until crisp; drain and crumble.
2. Peel and boil the potatoes in a pot of water until you can easily pierce a potato with a fork. You may steam potatoes also.
3. Drain fat. Cook onion and celery in fat until just tender. Blend in flour, sugar, salt, celery seed, and pepper to taste.
4. Add vinegar and water. Cook and stir until thickened and bubbly. Add bacon and potatoes; heat thoroughly, tossing lightly so as not to break up the potato slices.
5. Garnish with parsley and green onion. Can be served warm or chilled, but you taste the bacon fat a bit more when it's chilled.