Place the potatoes in a large pot of boiling water. Cover with the lid and turn the heat down to medium. Boil for 15-20 minutes until fully cooked through and can easily pierce through with a knife. Let the potatoes slightly cool then peel the skin off, if desired. Cut into ½-inch chunks and place into a large bowl.
In another bowl, whisk together the mayonnaise, Maille Whole Grain Mustard, relish, apple cider vinegar, and paprika. Season with salt and pepper to taste. Pour the dressing over the potatoes.
Add the red onion, celery, egg, and dill to the bowl with the potatoes. Mix until well combined and coated in dressing. Cover and refrigerate for 3-4 hours to chill. Serve chilled.