1. Place potatoes in a pot, cover them with water and bring to a boil. Cook for about 20 minutes, or until potatoes are easily pierced with a knife. Drain and let cool.
2. In the meantime, place eggs in a pot, fill it with cold water to cover the eggs. Bring the water to a boil. Reduce the heat and boil the eggs for 10 minutes to get hard boiled eggs. Chill them by placing under cold running water or in a bowl of ice water.
3. In a bowl, whisk together cold water and sour cream, add vinegar and salt, mix well. Put in the fridge.