In a large pot, cover potatoes with water and season with salt. Bring to a boil, reduce the heat and simmer until tender, about 10 minutes.
While the potatoes cook, place the bacon in a skillet over medium heat. Sauté the bacon until it just starts to crisp, about 7 minutes; you want to render the bacon slowly. Once the bacon has rendered some of its fat, add the yellow onions to the bacon and cook until softened, 3 to 4 minutes. Add the vinegar and mustard.
Once the potatoes are cooked, drain them and add immediately to the pan with the sautéed bacon. Stir to coat. Add the green onion and fresh herbs, toss to combine. Season with more salt and pepper if desired. Serve warm or at room temperature.
Cook's Note: Tossing the potatoes with the dressing while they are still hot helps them absorb the flavors.