Chop the potatoes into 2” pieces and place them in saucepan. Cover with water and heat over high until boiling. Turn the heat down to medium and continue to boil for about 20 minutes or until you can stick a fork in one and it breaks apart. Remove the potatoes from the heat and drain off the excess water. Stir in the sour cream, dill, chives and vinegar. Continue to stir until it resembles really lumpy mashed potatoes. Norwegian potato salad is usually used as a spread and not as a side dish, so you want it smooth enough to spread on bread, but not as smooth as mashed potatoes. Serve hot or chilled in place of mayonnaise on a sandwich or top your hotdog with potetsalat and crispy fried onions.