Preheat the air fryer to 380°F while you prep the potatoes.
Slice potatoes into 1/4-inch sticks. Rinse, then soak in cold water for 10 minutes.
Drain and dry the potatoes very well with clean towels.
Toss fries with olive oil, cornstarch, garlic powder, salt, pepper, and paprika until evenly coated.
Air fry in a single layer for 15–18 minutes, shaking the basket every 5 minutes, until crispy and golden.
Transfer hot fries to a bowl. Immediately toss with Parmesan and parsley. Adjust salt and add red pepper flakes if desired. Serve at once.