Begin by washing the potatoes thoroughly. Place them in a large pot and cover with cold water. Bring to a boil over medium-high heat. Once boiling, reduce the heat to medium and cook for about 15-20 minutes, or until the potatoes are fork-tender. Drain and let them cool slightly.

While the potatoes are cooling, prepare the dressing. In a large mixing bowl, combine the mayonnaise, Dijon mustard, apple cider vinegar, salt, and black pepper. Mix until well combined.

Once the potatoes are cool enough to handle, peel them if desired (the skin can be left on for added texture) and cut them into bite-sized cubes. Add the potatoes to the bowl with the dressing.

Add the chopped celery, red onion, hard-boiled eggs, and sweet pickle relish (if using) to the bowl. Gently fold everything together until the potatoes are evenly coated with the dressing.

Taste and adjust seasoning if necessary. If the salad seems too dry, you can add a little more mayonnaise or a splash of vinegar for extra flavor.

Cover the bowl with plastic wrap and refrigerate for at least 1 hour before serving to allow the flavors to meld.

Before serving, sprinkle with fresh dill or parsley if desired for a pop of color and flavor.