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. Drain and let cool slightly.
02 - In a large mixing bowl, whisk together mayonnaise, sour cream, Dijon mustard, apple cider vinegar, lemon juice, sugar, salt, and black pepper until smooth.
03 - Add cooled potatoes, celery, red onion, dill, chives, and parsley to the dressing. Gently fold to combine, ensuring potatoes are evenly coated.
04 - If using, fold in chopped hard-boiled eggs gently to incorporate.
05 - Taste and adjust seasoning with additional salt and black pepper as needed.
06 - Cover and refrigerate for at least 1 hour to allow flavors to meld.
07 - Garnish with extra fresh dill and serve chilled or at room temperature.