Place the potatoes in a large pot, cover with cold water, and bring to a gentle boil. Cook until the potatoes are tender when pierced with a fork, about 15-20 minutes. Drain thoroughly and let cool slightly.
While the potatoes are still warm, peel off the skins using a peeler or your fingers, which will be easier as the flesh loosens. Be careful as the potatoes can be hot—use a towel or tongs if needed.
Cut the peeled potatoes into bite-sized chunks and transfer them to a large mixing bowl. Gently mash some of the pieces if you prefer a slightly creamier texture, but leave enough whole for texture.
Add the mayonnaise and apple cider vinegar to the potatoes. Use a silicone spatula to fold everything together gently, ensuring the dressing coats the potatoes evenly without breaking them apart.
Stir in the thinly sliced red onion, chopped parsley, and finely chopped celery, distributing the ingredients throughout the salad. The onions should add a sharp bite, while the herbs bring freshness and the celery crunch.
Season the salad with salt and pepper to taste. Tasting and adjusting the seasoning at this stage helps bring out the flavors perfectly.
Cover the bowl and refrigerate the potato salad for at least 30 minutes to let the flavors meld. Serve chilled, garnished with additional herbs if desired.
