4 4lbred potatoes 0.33333333333333lbbacon, diced 2medium onions, finely minced 0.5cwhite wine vinegar, plus more to taste 5.5tsugar 2tcornstarch 0.75cwater 0salt and pepper to taste 1egg, beaten 1Tchopped fresh chives, for garnish Fill a large pot two-thirds full with water, add salt and bring to a boil. Cook potatoes with skins on until just past crunchy, about 7 or 8 minutes. Drain and set aside. Put the bacon and onions in a large, heavy skillet, and cook over moderate heat until the onion softens but does not brown, about 6 minutes. Add the vinegar and sugar to the skillet and bring to a boil over high heat. Mix the cornstarch with a few teaspoons of the water and make a smooth paste. Add the cornstarch paste to the skillet and mix well, scraping the bottom of the pan with a wooden spoon. Add the remaining water and return to a boil. Turn the heat down to low and continue to cook for 10 minutes, or until the mixture has a velvety texture. When the potatoes are cool enough to handle, peel them, cut them into 1/4-inch slices, and place them in a large mixing bowl. Sprinkle with salt and pepper to taste. Pour the bacon and onion mixture, along with the beaten egg, over the potatoes. Gently mix all ingredients well; do not break the potato slices. Mix in a little additional vinegar to taste. Sprinkle salad with chives and serve warm.