Start by peeling and cubing the Yukon gold potatoes into bite-sized pieces. Place them in a large pot filled with salted water and bring to a boil. Cook for 12 to 16 minutes, or until they are fork-tender but not falling apart.

While the potatoes are cooling, preheat your oven to 400°F (200°C). Line a baking sheet with aluminum foil to prevent sticking and for easy cleanup.

In a large mixing bowl, toss the boiled Yukon gold potatoes with olive oil and garlic powder. Ensure all pieces are evenly coated, and sprinkle with kosher salt and freshly cracked pepper.

Spread the seasoned potatoes in a single layer on the prepared baking sheet. Roast in the preheated oven for about 30 minutes, or until the potatoes are very brown and crispy, shaking the pan halfway through for even cooking.

While the potatoes are roasting, prepare the dressing in a large mixing bowl. Combine the sour cream, mayonnaise, reserved scallions, dill, parsley, Dijon mustard, and lemon juice. Mix until well blended.

Taste your dressing and season with kosher salt and pepper according to your preference.

Once the potatoes are perfectly roasted and crispy, remove them from the oven and let them cool for a few minutes. Toss the warm potatoes with the prepared dressing just before serving.