01 - Place potatoes in a large pot, cover with cold salted water, and bring to a boil. Reduce heat and simmer for 10 to 12 minutes, or until fork-tender. Drain and let 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 the warm potatoes to the dressing and toss gently to coat evenly.
04 - Fold in celery, red onion, scallions, dill, hard-boiled eggs, and pickles if using. Mix gently to combine all ingredients.
05 - Taste the salad and adjust salt and pepper as needed.
06 - Cover and refrigerate for at least one hour to develop flavors before serving.