Place the sliced potatoes in a large saucepan and add enough cold water to cover them by 2 inches. Stir in 2 tablespoons of kosher salt and bring to a boil over high heat.

Reduce the heat to a simmer and cook for 10 to 12 minutes, until the potatoes are just barely tender when pierced with a fork. Reserve 1/3 cup of the cooking liquid, then drain the potatoes and transfer them to a large bowl.

Drizzle the hot potatoes with the white wine vinegar and the reserved cooking liquid. Let them stand for 10 minutes, tossing occasionally, so they absorb the flavors.

While the potatoes cool, combine the celery, shallots, cornichons, chives, and dill in a medium bowl. Set aside.

In a small bowl, whisk together the mayonnaise, sour cream, 1 teaspoon salt, and 1/2 teaspoon pepper until smooth.

Add three-quarters of the vegetable-herb mixture to the potatoes, reserving the rest for later. Pour the mayonnaise dressing over the top and stir gently to combine, making sure to incorporate any liquid at the bottom of the bowl. Let the salad cool to room temperature, then cover and refrigerate for at least 2 hours, or overnight, to let the flavors meld.

Just before serving, add the reserved vegetable-herb mixture and the diced hard-boiled eggs to the chilled potato salad. Sprinkle with extra fresh dill, a pinch of salt, and a grind of pepper. Stir gently to combine. Taste and adjust seasoning if needed. Serve cold or at room temperature.