Peel and cut potatoes into ¾-inch chunks. Place in a large pot with 6 cups of cold water. Add 1 ½ teaspoons salt. Bring to a boil.
Add vinegar. Boil for 10-12 minutes or until potatoes can be easily pierced with a fork.
Drain well. Allow to cool for 10 minutes. Pat dry with paper towels before adding to other ingredients.
Combine Boursin, mayonnaise, sour cream, black pepper, ¼ teaspoon salt, and mustard in a medium bowl.
Transfer potatoes to a large mixing bowl. Add Boursin/mayo mixture, onion, celery, and pickles. Stir until just combined.
Add eggs, dill, and chives. Gently combine. Reseason to taste. Chill until ready to serve.
Makes 8 servings.