Place the potatoes in a large saucepan with water to cover them by two inches and two tablespoons of salt. Bring to a boil then simmer for 10 to 12 minutes until tender.
Scoop out and set aside ⅓ cup of the cooking liquid. Drain the potatoes and place them in a large bowl. Drizzle with vinegar and reserved cooking liquid, let stand for 10 minutes.
In a medium bowl, combine celery, shallots, cornichons, chives, and dill. In a small bowl, whisk together mayonnaise, sour cream, salt, and pepper.
Add three-quarters of the vegetable and herb mixture to the potatoes. Stir in the dressing. Refrigerate for at least two hours.
Before serving, add the reserved vegetable mixture and eggs to the salad. Sprinkle with extra dill, salt, and pepper. Serve cold or at room temperature.
