1. Begin by peeling and cutting the potatoes into even, bite-sized chunks. Bring a large pot of salted water to a boil, then add the potato cubes. Cook the potatoes until they are fork-tender, about 15-20 minutes. Drain the potatoes and allow them to cool completely before proceeding with the recipe.

2. In a large bowl, combine the cooled potatoes with the chopped onion, celery, and hard-boiled eggs. Gently toss the ingredients together, taking care not to mash the potatoes.

3. In a separate bowl, whisk together the mayonnaise, mustard, white vinegar, and a generous seasoning of salt and pepper. The dressing should have a smooth, creamy consistency.

4. Pour the prepared dressing over the potato mixture and gently fold it in until all the ingredients are evenly coated. Be sure to take your time and avoid overmixing, as you want to maintain the texture of the potatoes.

5. Cover the creamy potato salad and refrigerate it for at least 1 hour, allowing the flavors to meld. Before serving, top the salad with the sliced spring onions and a light dusting of paprika for a beautiful, appetizing presentation.