01 - Place potatoes in a large pot and cover with cold, salted water. Bring to a boil, then reduce heat and simmer for 10 to 12 minutes until just fork-tender. Avoid overcooking.
02 - Drain potatoes and spread on a baking sheet. Allow to cool for 10 minutes.
03 - In a large bowl, whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, sugar, kosher salt, and black pepper until smooth.
04 - Add cooled potatoes, celery, red onion, dill, and chives (if using) to the dressing. Gently toss to evenly coat all ingredients.
05 - Cover and refrigerate for at least one hour to allow flavors to meld.
06 - Just before serving, garnish with additional fresh dill sprigs.