Place the potatoes in a pot, cover with cold salted water and bring to a boil. Cook for 15–20 minutes, until a fork slides in easily.
Preheat the oven to 425°F. Drain the potatoes and let them steam dry in the colander for 5 minutes.
Brush a large rimmed sheet pan with 1 tablespoon of the olive oil. Arrange the potatoes on the pan with space between them.
Press down on each potato with the bottom of a glass or a potato masher until it’s about ½ inch thick.
Drizzle with the remaining 2 tablespoons oil and sprinkle with the garlic powder, salt and pepper.
Roast for 25–30 minutes, until deep golden and crisp at the edges. Sprinkle with parsley and serve.