01 - Place potatoes in a large pot, cover with cold salted water, bring to a boil, then simmer for 10 to 12 minutes until just fork-tender. Drain and allow to cool slightly.
02 - Whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, fresh dill, salt, and black pepper in a large bowl until smooth.
03 - Add the warm potatoes, celery, red onion, and scallions to the dressing and gently toss until evenly coated.
04 - Fold in chopped hard-boiled eggs and diced pickles if using.
05 - Cover and refrigerate for at least 1 hour to develop flavors.
06 - Before serving, adjust seasoning as needed and garnish with additional dill if desired.