Place potatoes in a large pot with enough water to cover by several inches. Bring to a boil over high heat, add 1 tablespoon salt, and reduce to a gentle boil. Cook until potatoes are just tender when pierced with a knife. Do not overcook.
Drain, cool, and transfer to a bowl.
While the potatoes cook, combine the vinegar, sugar, and remaining salt in a small saucepan and place over medium heat until sugar is dissolved.
Drizzle over the potatoes, and gently toss to coat.
Saute bacon in a large skillet placed over medium-low heat, stirring frequently until browned and crisp.
Remove with a slotted spoon; drain on paper towels.
Drain excess fat from skillet, leaving a thin coat of bacon grease in skillet.
Saute onions in skillet with the reserved bacon grease until translucent but not browned.
Pour in the beef broth and bring to a boil over high heat. Reduce heat to a simmer and cook until reduced by half; about 20 minutes.
Pour the broth mixture over the potatoes, and sprinkle with the bacon and chopped parsley. Gently stir, and serve immediately.
