Boil the potatoes for 20-25 min. Meanwhile preheat the oven to 450* with a large cookie sheet in it.
Drain the potatoes for 5 minutes. Meaning, allow them to sit in a colander draining for the full 5 minutes.
Remove the (hot!) cookie sheet from the oven and place on a level, heat-proof surface. Drizzle garlic olive oil on the cookie sheet and spread evenly to coat.Smash the potatoes into the cookie sheet with a sturdy fork. Let the smashed potatoes sit outside of the oven for 5 minutes.
Drizzle the potatoes with the garlic olive oil. Salt and pepper to taste. Sprinkle with the Parmesan cheese, if using.
Bake for 30-45 minutes in the middle rack of the oven. DO NOT FLIP. Potatoes are done when they have some crispy, golden brown edges.
Notes
For vegan and dairy free, omit the parmesan cheese.