Place the potato chunks in a large pot and cover with water by at least two inches. Add about 1 tablespoon of salt to the water for flavor.
Bring the pot of water to a boil. Once the water is boiling, boil the potatoes for 7-9 minutes until just tender but not mushy. Drain the potatoes and let cool slightly.
Meanwhile, add the bacon to a skillet over medium heat. Let the bacon warm and begin to sizzle.
When the bacon is warm but not fully cooked (after about 3 minutes), add the diced onion to the skillet. Stir for 3-5 minutes until the onion has softened and browned slightly, then turn the heat off the skillet.
To the hot bacon and onion mixture, add the stock, vinegar, sugar, and salt. Whisk the dressing and immediately pour over the still-warm potatoes, OR toss the potatoes with the dressing directly in the skillet.
Stir the potatoes gently with the dressing and taste; add more salt or vinegar to your preference. The salad should be very flavorful.
Top with the sliced scallions and serve. This salad is best served slightly warm or at room temperature. Enjoy!