01 - Preheat the oven to 425°F. Line a baking sheet with parchment paper or lightly grease it.
02 - Place the potatoes in a large pot and cover with cold, salted water. Bring to a boil, reduce heat, and simmer for 15–20 minutes, or until the potatoes are fork-tender. Drain well.
03 - Arrange the potatoes on the prepared baking sheet. Using the bottom of a glass or potato masher, gently smash each potato to about 1/2-inch thick.
04 - In a small bowl, mix melted butter, olive oil, and minced garlic. Brush the smashed potatoes generously with the garlic butter mixture.
05 - Sprinkle potatoes evenly with salt, pepper, and grated Parmesan cheese.
06 - Bake for 20–25 minutes, or until the edges are golden and crispy.
07 - Remove from the oven and sprinkle with fresh chives. Serve hot.