Pat the chicken thighs completely dry with paper towels. This is the most important step for achieving maximum crispiness. Moisture on the skin will cause the chicken to steam rather than fry.
Place the chicken thighs in a large bowl. Drizzle with olive oil and toss to coat. In a small ramekin, mix the garlic powder, onion powder, paprika, salt, and pepper. Rub the seasoning mixture evenly over both sides of the chicken, making sure to get under the skin if possible.
Preheat your air fryer to 400°F (200°C) for about 3 minutes. Place the seasoned chicken thighs in the air fryer basket in a single layer, skin-side down. Do not overcrowd the basket; cook in batches if necessary.
Cook the chicken at 400°F (200°C) for 12 minutes. Flip the chicken thighs so the skin side is now facing up. This allows the fat to render and the skin to crisp up perfectly.
Sprinkle the grated Parmesan cheese generously over the top of each chicken thigh. Continue to air fry for another 8 to 10 minutes, or until the internal temperature reaches 165°F (74°C) and the cheese is golden and melted.
Remove the chicken from the air fryer and let it rest for 5 minutes. This helps the juices redistribute. Sprinkle with fresh parsley before serving.