Start by placing the small white potatoes into a large pot and covering them with water. Add 2 tablespoons of salt, bring to a boil, then lower the heat and let simmer until tender, approximately 10 to 15 minutes.

Drain the potatoes in a colander. Return the colander to the pot and cover with a clean kitchen towel, allowing the potatoes to steam for 15 to 20 minutes to help dry them.

In a separate small bowl, whisk together the mayonnaise, buttermilk, Dijon mustard, whole grain mustard, chopped dill, and a teaspoon each of salt and pepper. Set aside this flavorful dressing.

Once the potatoes are cool enough to handle, cut them into quarters or halves, as needed. In a large mixing bowl, drench the warm potatoes with the prepared dressing. Mix in the celery, red onion, and additional seasonings to taste, tossing gently.

Cover the bowl and refrigerate for a few hours to allow the flavors to develop together. This salad can be served chilled or at room temperature, complementing grilled dishes beautifully.