Wash the potatoes thoroughly and pat them completely dry with a clean kitchen towel. Cutting them into uniform sizes—either halves or quarters depending on their size—ensures they all cook at the same rate.
In a large mixing bowl, combine the cut potatoes, olive oil, garlic powder, onion powder, salt, and black pepper. Toss everything together until every piece of potato is evenly coated with the oil and spices.
Preheat your air fryer to 400°F (200°C) for about 3 minutes. Place the seasoned potatoes into the air fryer basket in a single layer. It is okay if they overlap slightly, but do not overcrowd the basket if you want maximum crispiness.
Cook the potatoes for 15 to 20 minutes. About halfway through the cooking time, remove the basket and give it a good shake to ensure even browning. The potatoes are done when they are fork-tender and the skins are golden brown.
Once the potatoes are cooked, immediately sprinkle the grated Parmesan cheese over them while they are still in the hot basket or move them to a bowl and toss. The residual heat will melt the cheese perfectly. Garnish with fresh parsley before serving.