01 - Place potatoes in a large pot and cover with cold salted water. Bring to a boil, then simmer for 10 to 12 minutes until fork-tender. Drain and let cool slightly.
02 - In a large bowl, whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, dill, salt, and black pepper until smooth.
03 - Add cooked potatoes, celery, red onion, and scallions to the dressing. Gently toss until well coated.
04 - If using, fold in chopped hard-boiled eggs and diced pickles.
05 - Cover and refrigerate for at least 1 hour to allow flavors to meld.
06 - Taste and adjust seasoning before serving. Garnish with extra dill if desired.