01 - Place potatoes in a large pot, cover with cold salted water, and bring to a boil. Reduce heat and simmer 10 to 12 minutes until fork-tender. Drain and allow to cool slightly.
02 - In a large bowl, whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, sugar, salt, and black pepper until smooth.
03 - Add warm potatoes to the dressing and gently toss to coat evenly.
04 - Fold in diced celery, red onion, scallions, chopped dill, hard-boiled eggs, and pickles if using. Mix gently to combine.
05 - Taste the mixture and adjust seasoning with additional salt, pepper, or vinegar as desired.
06 - Cover and refrigerate for at least one hour to allow flavors to meld before serving.