Add potatoes to large pot and cover with water. Bring to a boil and cook until fork-tender, about 15-20 minutes depending on size. Drain the potatoes thoroughly and allow to dry for 3-5 minutes.

Meanwhile, preheat oven to 425°F. Coat one or two baking sheets generously with with cooking spray.

Combine 2 tablespoons of olive oil with the melted butter, salt, pepper, garlic powder and paprika in a small bowl.

Divide the potatoes between the baking sheets. Using a flat-bottomed tool (like a measuring cup or glass), gently smash each potato to your desired thickness. Potatoes should be in a single layer so they crisp evenly. Allow the steam to escape and dissipate, then brush the butter-oil mixture onto each potato.

Roast for 30-35 minutes, until edges are golden brown and crispy. When they are almost done, sprinkle grated parmesan over each potato and bake for an additional 5 minutes or until the cheese melts and crisps up.

Meanwhile, In a small bowl, combine sour cream, chives, garlic and onion powders. Whisk enough milk to achieve to your desired consistency. Taste and season with salt and pepper.

Transfer the potatoes to a serving platter and garnish with fresh chives. Nestle in the sour cream sauce for serving.