Boil Potatoes: In a large pot, place cubed Yukon gold potatoes and cover with cold water. Add 1 tablespoon of kosher salt, bring to boil, and cook until tender, about 12-16 minutes. Drain and cool slightly.

Prepare to Roast: Preheat oven to 400°F (200°C). Line a baking sheet with aluminum foil.

Season Potatoes: Toss potatoes with olive oil, garlic powder, salt, and pepper in a large bowl until evenly coated.

Bake for Crispiness: Spread potatoes in a single layer on the baking sheet and roast for about 30 minutes, turning halfway, until golden and crispy.

Make Dressing: Whisk together sour cream, mayonnaise, scallions, dill, parsley, Dijon mustard, and lemon juice. Season with salt and pepper.

Combine and Serve: Toss warm potatoes with dressing just before serving. Garnish with reserved scallions, dill, and parsley.