Preheat oven to 450 degrees F (230 degrees C).

Cover a large baking sheet pan with foil, give a light coat of vegetable oil over the pan. Then place washed potatoes onto sheet pan and drizzle the tops of the potatoes with more oil to lightly coat. Sprinkle generously with kosher salt. Roast potatoes in the preheated for 35-40 minutes, or until potatoes are fork tender.

Using a potato masher, the bottom of a glass or mug, or a large serving fork, press the potatoes so that they flatten and break open. It's okay if they break apart a little, that makes for more crispy edges.

Put the minced garlic, red pepper flakes, about ½ teaspoon of black pepper, and salted butter in a small microwave-safe bowl, and microwave for 30 seconds to 1 minutes, until butter is melted. Brush tops of potatoes with the garlic butter generously and evenly.

Roast potatoes for about 10-15 minutes or until tops start to turn golden brown and crispy.

Sprinkle the garlic butter smashed potatoes with parmesan and place back into the oven. Turn the broiler on low heat (or high, if you watch cautiously) for 2-3 minutes or until cheese is melted and browned a little.

Remove potatoes from oven and give a little seasoning with a generous pinch of salt and pepper to taste. Let potatoes cool slightly before serving.