Trim the stem ends of the Brussels sprouts, remove any loose outer leaves, and cut them in half.
Place the halved Brussels sprouts in a large bowl and drizzle them with olive oil. Toss to ensure they are evenly coated.
Sprinkle the minced garlic over the Brussels sprouts and season with salt and pepper according to your taste. Toss again to distribute the seasonings evenly.
Preheat your air fryer to 375°F (190°C) for 3-5 minutes.
Once the air fryer is preheated, transfer the seasoned Brussels sprouts to the air fryer basket in a single layer. You may need to cook them in batches if your air fryer is small.
Air fry the Brussels sprouts for 15-20 minutes, shaking the basket or tossing them with tongs every 5 minutes to ensure even cooking. They should be golden brown and crispy on the outside and tender on the inside.
In a microwave-safe bowl, melt the unsalted butter in the microwave. Once the Brussels sprouts are done, drizzle the melted butter over them while they are still hot. If desired, sprinkle with shredded Parmesan.
Transfer the garlic butter-coated Brussels sprouts to a serving dish, and enjoy immediately as a delightful side dish.