Place a rack in the bottom third of oven; preheat oven to 450°. Place 2 lb. small yellow potatoes in a large pot, cover with water, and generously season with kosher salt; bring to a boil over high heat. Reduce heat to medium; simmer until potatoes are fork tender, 15–20 minutes. Drain and transfer potatoes to a rimmed baking sheet lightly drizzle in extra-virgin olive oil. Let cool slightly. In a small bowl mix together 1½ tsp. Diamond Crystal salt or ¾ tsp. Morton kosher salt, 2 tsp. garlic powder, and 1½ tsp. freshly ground black pepper. Using the bottom of a glass or lightly oiled measuring cup, smash each potato to a roughly ½-inch to ¾-inch  thickness. Drizzle the tops with 2 Tbsp. extra-virgin olive oil and sprinkle the top with half of the seasoning mixture. Flip potatoes (it’s OK if they fall apart - that’s part of the beauty), drizzle with the remaining 2 Tbsp. extra virgin olive olive, and season with the remaining seasoning mixture. Roast potatoes, flipping them halfway through with a thin spatula (again, it’s OK if they fall apart), until crispy and dark golden brown, about 40 to 50 minutes total. Sprinkle the tops with finely grated Parmesan and finely chopped fresh parsley leaves before serving, if desired. Cooks’ note: Small waxy yellow potatoes are ideal here, but any petite potato would do the job. If using very small potatoes, such as fingerlings, you might just need to adjust the cooking time.