• Preheat your oven to 400°F and place a rack in the middle. Line a rimmed baking sheet with parchment paper.

Prepare the Olive Oil Mixture:

• In a large bowl, combine the olive oil, grated garlic, kosher salt, pepper, cayenne (if using), and parsley (if using). Stir until well mixed.

Prepare the Potatoes:

• Cut each potato in half, adding them to the olive oil mixture as you go to prevent browning. Toss the potatoes in the mixture until they are fully coated.

Add the Parmesan:

• Add the grated Parmesan to the bowl with the potatoes and toss gently, ensuring the potatoes are just coated with the cheese to avoid clumping and losing cheese off the potatoes.

Roast the Potatoes:

• Arrange the potatoes on the prepared baking sheet in a single layer with the cut side facing down. As you place the potatoes, scrape any remaining Parmesan mixture onto the flat sides of the potatoes. It's fine if the potatoes are close together.
• Roast the potatoes for 25 to 35 minutes, or until they are fork-tender and the Parmesan has turned a deep golden brown. Rotate the pan halfway through the cooking time.

Finish and Serve:

• Once the potatoes are done, remove the baking sheet from the oven and let them sit for 5 minutes. This will allow the Parmesan to cool slightly and set, creating a crispy texture.
• Flip the potatoes over (you may need a thin metal spatula) to reveal the golden-brown, cheesy side, and transfer them to a serving platter. Top with more parsley, if desired, and serve immediately.

Storing Leftovers:

• If you have any leftovers, store them in an airtight container in the refrigerator for up to 4 days.

Reheating Leftovers:

• To reheat, preheat the oven to 375°F with a rack in the middle. Line a rimmed baking sheet with parchment paper and arrange the leftover potatoes cut side down. Reheat for 5 to 10 minutes until hot and the Parmesan has re-crisped. Alternatively, you can reheat them in the air fryer.