Trim ends off Brussels sprouts, cut in half lengthwise, and set aside any loose outer leaves.
Add Brussels sprouts to a bowl with oil, salt, pepper, and garlic powder, and toss until evenly coated.
Preheat the air fryer to 375℉.
Place Brussels sprouts in air fryer basket in a single layer, with cut side down where possible.
Air fry for 12-15 minutes, shaking basket halfway through, until deeply golden and crispy on edges and tender inside. Add excess leaves halfway through so they crisp up without burning.
While Brussels sprouts cook, whisk together honey, Dijon mustard, and vinegar in a small bowl.
Transfer hot Brussels sprouts to serving bowl.
Drizzle with honey Dijon glaze and toss gently to coat.
Taste and adjust with a small pinch of salt if needed.
Finish with Parmesan as desired, and serve immediately.