Bring 3 quarts water to a boil in a large saucepan; add potatoes and salt. Cook for 10 minutes or just until tender; drain. Sprinkle boiled potatoes with vinegar and set aside.
For the dressing, combine all ingredients except dill, parsley and chives in a blender or food processor. Puree until very smooth, about 1 minute. Add herbs and pulse 4 or 5 times, just until herbs are well minced. Dressing can be made up to 1 week ahead and refrigerated.
Pour dressing over potatoes and stir to coat. Garnish with additional herbs, if desired; serve immediately.