In a large pot, place the cut Yukon gold potatoes and cover them with cold water, adding 1 tablespoon of salt. Bring it to a boil over high heat and cook for about 12-16 minutes, until the potatoes are tender when pierced with a fork but not falling apart. Drain them well in a colander and set aside.

Preheat your oven to 400°F (200°C) while the potatoes are draining. In a large mixing bowl, combine the drained potatoes with olive oil, garlic powder, salt, and black pepper. Gently toss the potatoes until they are evenly coated.

Line a baking sheet with foil for easy cleanup, then spread the seasoned potatoes in a single layer. Roast them in the preheated oven for about 30 minutes, giving them a stirring halfway through.

While the potatoes are roasting, prepare the creamy dressing. In a medium bowl, combine sour cream, mayonnaise, chopped scallions, fresh dill, parsley, Dijon mustard, and freshly squeezed lemon juice. Whisk everything together until smooth, and season the dressing with salt and pepper to taste.

Once the potatoes are crispy and browned, remove them from the oven and let them cool slightly. Toss the hot roasted potatoes with the creamy dressing until they are fully coated. Garnish with reserved scallions, dill, and parsley.