Preheat the air fryer to 375°F (190°C) for 3 minutes if needed.Trim the ends of the Brussels sprouts and cut them in half.Toss them with olive oil, garlic powder, onion powder, paprika, salt, and pepper.Arrange the Brussels sprouts in a single layer in the air fryer basket.Cook for 8 minutes, shaking the basket halfway through.Sprinkle with Parmesan cheese and cook for another 2 minutes, until crispy and golden.Let rest for 2 minutes.Drizzle with balsamic glaze if desired, garnish with parsley, and serve immediately.