Mix the olive oil, salt, pepper, and garlic powder in a bowl.
Drizzle and spread oil on a parchment-lined sheet pan.
Scatter the Parmesan Mixture over the olive oil. Once sprinkled, do not touch - don't try to spread it.
Place potatoes cut side down, pressing firmly.
Drizzle the top of the potatoes with more olive oil or spray with oil, then sprinkle generously with salt.
Bake potatoes for 35 - 40 minutes or until they are soft and the parmesan crust is deep golden brown on the bottom.
Then place on the serving platter. Garnish with chopped parsley if desired.
Video
Notes
If adding fresh herbs at after the potatoes are roasted. Chopped rosemary, thyme, or parsley should be tossed in right after the potatoes come out of the oven. High heat can burn them and dull their flavor.
Make sure to use fresh grated Parmesan with a sand-like texture. I grate my own Parmesan-Reggiano because it has more flavor and it's delicious.. But you can find the sand-like grated parmesan in the deli area. Note that the pre-shredded Parmesan sold in the cheese aisles won't give you the same crispiness.
Don't peek too often. Every time you open the oven, it adds quite a bit more time to the overall cooking time because the oven has to reheat again.
If you're short on time, you can also microwave the potatoes for 2-3 minutes before roasting. This helps get the inside cooked faster, and you can cut down your bake time.