Place the potatoes into a pot, and fill it with enough water to cover them. Bring to a boil, and cook for about 10 minutes, or until easily pierced with a fork. Immediately drain, and set aside to cool slightly.
Using your preferred method fry the bacon until browned and crisp. Reserve the bacon grease.
Combine the bacon grease and onion in a large skillet, and cook over medium heat until the onions are translucent and just starting to brown.
Add the apple cider vinegar, water, sugar, and celery salt to the pan. Bring to a boil and stir until sugar is dissolved. If serving warm add the potatoes and half of the bacon to the pan and heat through, then transfer to a serving dish. Crumble the remaining bacon over the top, and serve warm. Top with fresh or dried parsley if desired.
To serve cold, pour the sauce and half the bacon over the top of the potatoes in a bowl. Stir to combine and refrigerate until ready to serve, sprinkle the remaining half of the bacon on top before serving.