01 - Preheat the oven to 425°F and line a baking sheet with parchment paper or grease lightly.
02 - Place potatoes in a large pot, cover with cold salted water, bring to a boil, then simmer for 15–20 minutes until fork-tender. Drain thoroughly.
03 - Arrange the potatoes on the prepared baking sheet and gently smash each to approximately 1/2 inch thickness using the bottom of a glass or potato masher.
04 - Combine melted butter, olive oil, and minced garlic in a small bowl.
05 - Brush smashed potatoes generously with the garlic butter mixture.
06 - Sprinkle evenly with kosher salt, black pepper, and grated Parmesan cheese.
07 - Bake for 20–25 minutes until edges are golden and crispy.
08 - Remove from oven, sprinkle fresh chives over the top, and serve hot.