o cook the potatoes, place them in a large pot of cold, salted water. Bring to a boil over high heat, then decrease the heat to medium-low. Simmer until the potatoes are tender, 10 to 15 minutes. Drain well in a colander. While still warm, transfer the potatoes to a rimmed baking sheet and drizzle with the vinegar. Set aside to cool to room temperature.

To make the dressing, combine the mayonnaise, sour cream, yogurt, and mustard in a large bowl. Season with salt and pepper.

To assemble the salad, add the cooled potatoes, onion, celery, and parsley to the dressing and stir to combine and coat. Taste and adjust for seasoning with salt and pepper. Serve at room temperature or chilled.