Wash the baby potatoes thoroughly. Place them in a large pot and cover them with water. Add a pinch of salt and bring to a boil over medium-high heat.
Once boiling, reduce the heat and let the potatoes simmer for about 15-20 minutes, or until they are fork-tender. Be careful not to overcook them.
While the potatoes are cooking, prepare the dressing. In a mixing bowl, whisk together the mayonnaise, Dijon mustard, apple cider vinegar, salt, and black pepper until smooth.
After the potatoes are cooked, drain them in a colander and let them cool for about 10 minutes. Once cooled, chop the potatoes into bite-sized pieces.
In the large mixing bowl, combine the chopped potatoes, diced celery, finely chopped red onion, and fresh parsley. If using, add the chopped hard-boiled eggs.
Pour the dressing over the potato mixture and gently fold everything together until the potatoes are well-coated.
Taste and adjust the seasoning if necessary. Cover the bowl with plastic wrap and refrigerate the potato salad for at least 30 minutes before serving to allow the flavors to meld.
Serve chilled, and enjoy your creamy potato salad!