01 - Set oven temperature to 425°F and prepare a baking sheet by lining it with parchment paper.
02 - Place potatoes in a large pot, cover with cold water, add a pinch of salt, bring to a boil, then reduce heat and simmer for 15 to 20 minutes until fork-tender.
03 - Drain the potatoes and let them rest for 5 minutes to cool slightly.
04 - Arrange potatoes on the prepared baking sheet and gently flatten each to approximately 1/2 inch thickness using the bottom of a glass or a potato masher.
05 - Combine olive oil, minced garlic, sea salt, and ground black pepper in a small bowl, then drizzle evenly over the smashed potatoes.
06 - Bake the potatoes for 20 to 25 minutes until they develop a golden-brown, crispy exterior.
07 - Remove potatoes from oven, drizzle with melted butter, sprinkle Parmesan cheese evenly over top, and return to oven for 3 to 5 minutes until cheese melts and lightly browns.
08 - Transfer to a serving dish, garnish with fresh chives, and serve immediately.