Combine the potatoes with 6 cups salted water in a medium saucepan.

Bring to a boil, then reduce the heat and simmer until the potatoes are tender, 5 to 10 minutes. Reserve 1/4 cup of the cooking liquid and drain. Transfer the potatoes to a large mixing bowl and keep warm.

Meanwhile, in a large skillet, cook the bacon over medium heat until brown and crisp, about 4 minutes. Remove the bacon with a slotted spoon and transfer to the bowl with the potatoes. Drain off all but 2 tablespoons of the bacon grease.

Add the shallot to the skillet and cook until slightly softened, about 3 minutes. Stir in the reserved cooking liquid, oil, vinegar and sugar. Bring to a boil. Pour the mixture over the potatoes and toss to coat.

Add the celery, parsley, and salt and pepper to taste. Mix well. Serve immediately.