Step 1: Place the cubed potatoes in a large pot and cover with cold water. Add a teaspoon of salt.
Step 2: Bring the pot to a boil, then simmer for 10-15 minutes until the potatoes are fork-tender but still hold their shape.
Step 3: Drain the potatoes thoroughly in a colander. While they are still warm, drizzle with apple cider vinegar and toss gently.
Step 4: In a small bowl, whisk together the mayonnaise, yellow mustard, and Dijon mustard until smooth.
Step 5: In a large mixing bowl, combine the cooled potatoes with the celery, red onion, relish, and chopped eggs.
Step 6: Pour the mustard dressing over the potato mixture and fold gently with a spatula until evenly coated.
Step 7: Season with salt and pepper. Cover and refrigerate for at least 4 hours before serving to allow flavors to meld.
Step 8: Garnish with fresh chives or a sprinkle of paprika before serving.