Place the potatoes in a large pot and add enough cold water to cover them by about 1 1/2 inches. Stir in 1 teaspoon of salt for every quart of water used.

Set the pot over high heat and bring to a boil, then lower the heat to a gentle simmer. Cooking at a simmer instead of a rolling boil keeps the potatoes from knocking into each other and breaking. Cook for 15 to 20 minutes, until a fork slides in easily.

While the potatoes cook, prepare an ice bath by filling a medium bowl with ice and cold water. Set it aside.

Drain the cooked potatoes and move them right away to the ice bath. Let them cool just until you can handle them, but they should still be warm inside. Cut the potatoes into bite-size chunks and put them in a large mixing bowl. Sprinkle the vinegar over the warm potatoes and season lightly with salt.

In a small bowl, whisk together the mayonnaise, sour cream, and mustard until smooth and creamy.

Pour the dressing over the potatoes, then add the chopped celery, pickles, parsley, dill, and chives. Stir gently with a spatula so the potatoes stay chunky and don't turn to mush.

Taste the salad and adjust with additional salt and pepper. If time allows, refrigerate for at least 30 minutes before serving to let the flavors blend. The salad is even better after a short chill.