01 - Place the potatoes in a large pot and cover with cold, salted water. Bring the water to a boil, then reduce the heat and simmer for 10–12 minutes, or until the potatoes are just fork-tender. Ensure not to overcook them.
02 - Drain the cooked potatoes thoroughly and spread them evenly on a baking sheet to cool for 10 minutes.
03 - In a large mixing bowl, whisk together the mayonnaise, sour cream, Dijon mustard, apple cider vinegar, sugar, kosher salt, and black pepper until the mixture is completely smooth and well combined.
04 - Add the cooled potatoes, finely diced celery, red onion, chopped fresh dill, and chives (if using) to the prepared dressing. Gently toss all ingredients together to ensure they are evenly coated.
05 - Taste the potato salad and adjust the seasoning as needed to your preference. Cover the bowl and refrigerate for at least 1 hour to allow the flavors to meld and deepen.
06 - Just before serving, garnish the creamy potato salad with additional fresh dill sprigs.