Place the chopped red potatoes in a large pot and cover them with cold, salted water. Bring the water to a boil over medium-high heat, then reduce the heat and simmer for 15-20 minutes, or until the potatoes are fork-tender.

Drain the potatoes thoroughly in a colander and allow them to cool completely to room temperature.

In a large mixing bowl, whisk together the mayonnaise, sour cream, Dijon mustard, fresh dill, fresh parsley, salt, and black pepper until the dressing is smooth.

Add the cooled potatoes and diced red onion to the bowl with the dressing. Gently toss the mixture until all the potatoes are evenly coated.

Cover the bowl securely and refrigerate the potato salad for at least 1 hour before serving to allow the flavors to meld.