01 - Place the 1 1/2 pounds of potatoes in a large pot and cover generously with cold, salted water. Bring the water to a rolling boil over high heat, then reduce to a simmer and cook until the potato chunks are fork-tender, which typically takes about 10 to 12 minutes. Carefully drain the cooked potatoes using a colander and allow them to cool slightly.
02 - In a large mixing bowl, vigorously whisk together the 3/4 cup mayonnaise, 2 tablespoons sour cream, 2 teaspoons Dijon mustard, 2 teaspoons apple cider vinegar, 1/2 teaspoon kosher salt, 1/4 teaspoon freshly ground black pepper, and 1/2 teaspoon granulated sugar until the mixture is completely smooth and well combined.
03 - Add the slightly cooled potatoes, finely diced celery, finely diced red onion, coarsely chopped hard-boiled eggs, finely chopped fresh parsley, and the optional finely diced dill pickles to the prepared dressing in the large bowl. Gently fold all ingredients together using a spatula until everything is evenly coated with the creamy dressing.
04 - Taste the potato salad and adjust the seasoning as needed, adding more salt or pepper to achieve your preferred flavor profile. Cover the bowl securely and refrigerate for a minimum of 1 hour to allow the distinct flavors to thoroughly meld and deepen, enhancing the overall taste.
05 - Serve the creamy potato salad chilled or at a cool room temperature. For an appealing presentation, garnish with additional fresh parsley, if desired, just before serving.