Place the potatoes in a medium saucepan, cover generously with water and season well with salt. Bring to a boil, then reduce to a simmer and cook until the potatoes are fork-tender, about 20 minutes. Drain and reserve.
Lightly coat a large straight-sided saute pan with olive oil. Toss in the bacon and bring the pan to medium heat. When the bacon is brown and crispy, toss in the onion and cook until very soft and aromatic, 7 to 8 minutes. Add the stock and vinegar.
Toss in the potatoes while they are still warm and cook until the liquid is absorbed, about 8 minutes. Taste and season with salt if needed. Toss in the chives and serve warm or at room temperature.
Photograph by Steve Giralt