01 - Set the oven to 425°F. Line a large baking sheet with parchment paper or apply a light coating of grease.
02 - Place potatoes in a large pot and cover with cold water. Add kosher salt and bring to a boil. Cook until fork-tender, approximately 15 to 20 minutes. Drain thoroughly.
03 - Transfer potatoes to the prepared baking sheet. Gently press each potato to about ½-inch thickness using the bottom of a glass or a potato masher.
04 - Combine olive oil, minced garlic, black pepper, and sea salt in a small bowl. Evenly drizzle this mixture over the smashed potatoes.
05 - Bake for 20 to 25 minutes until edges are golden and crispy.
06 - Remove from oven; drizzle melted butter and sprinkle grated Parmesan evenly over the potatoes. Return to the oven for 2 to 3 minutes until the cheese melts.
07 - Sprinkle fresh chopped parsley over the potatoes before serving.