01 - Place potatoes in a large pot and cover with cold, salted water. Bring to a boil, reduce heat, and simmer for 10 to 15 minutes until just fork-tender. Drain and let cool slightly.
02 - In a large bowl, whisk together mayonnaise, Dijon mustard, apple cider vinegar, whole-grain mustard if using, salt, black pepper, and paprika.
03 - Add cooled potatoes, celery, red onion, scallions, and parsley to the dressing. Gently fold to coat evenly.
04 - If desired, fold in chopped hard-boiled eggs and diced dill pickles.
05 - Adjust seasoning to taste. Cover and refrigerate for at least 1 hour to meld flavors.
06 - Optionally garnish with additional parsley and a sprinkle of paprika before serving.