How to Make It
In a large saucepan, cover the potatoes with water, season generously with salt and bring to a boil. Simmer over moderate heat until the potatoes are tender, about 25 minutes. Drain and let cool slightly, then peel the potatoes and cut them into 1/2-inch pieces. Transfer the potatoes to a large bowl and toss with the melted butter.
Meanwhile, in a small skillet, cook the bacon over moderate heat until browned and crisp, about 6 minutes. Drain on paper towels and crumble into small pieces. Wipe out the skillet.
Add the cream to the skillet and bring to a boil. Remove from the heat and stir in the vinegar. Pour the cream over the potatoes, add the onion and chives and fold together gently. Season with salt and pepper and serve warm.