Place the diced potatoes in a large pot and cover them with cold water. Bring to a boil over high heat, then cook until the potatoes are just fork-tender—soft but not falling apart. Drain the water and allow the potatoes to cool to room temperature.

Meanwhile, in a small mixing bowl, whisk together the mayonnaise, mustard, seasoned salt, vinegar, and a few cracks of black pepper. This forms the creamy, tangy dressing.

Take three of the hard-boiled eggs and cut them in half. Remove the yolks and mash them with a fork until smooth and crumbly. Stir the mashed yolks into the prepared dressing to enrich the texture and flavor. Chop the remaining egg whites and the five whole hard-boiled eggs into small pieces.

In a large mixing bowl, combine the cooled potatoes, chopped eggs, celery, and minced onion. Pour the dressing over the top and gently fold the mixture together until well-coated and cohesive. Taste and adjust with extra salt or black pepper if needed.

Transfer the salad to a serving dish, sprinkle generously with paprika for color and added flavor, and serve chilled or at room temperature.