Preheat the oven to 400°F (207°C).
Place each potato on a wooden spoon and cut horizontal slits into the potatoes. In a small bowl, combine the butter, garlic, garlic powder, salt, black pepper, and parsley. Stir to mix well. Toss the potatoes with the garlic butter mixture until they are well coated. Brush the garlic butter inside the slits of the potatoes. Transfer the potatoes to a cast-iron pan or roasting pan.
Roast the potatoes for 20 minutes, then turn them over and baste with the garlic butter mixture in the pan. Roast for an additional 20 minutes. Remove from the oven and serve immediately.
