Rinse the pound of Brussels sprouts thoroughly under cool running water. Pat the sprouts completely dry using a clean kitchen towel or paper towels. Moisture is the enemy of crispiness in the air fryer.

Trim the tough bottom end off of each Brussels sprout. Remove any loose, yellowed, or damaged outer leaves and discard them. Cut all the prepared Brussels sprouts in half lengthwise. If any sprouts are very large, quarter them to ensure even cooking.

Place the trimmed and halved Brussels sprouts into a large mixing bowl. Drizzle the 2 tablespoons of olive oil over the sprouts and toss well until every piece is lightly coated in oil.

In a small separate bowl, combine the kosher salt, black pepper, garlic powder, and onion powder (if using). Sprinkle the seasoning mixture evenly over the oiled Brussels sprouts, then toss vigorously again for approximately 30 seconds to ensure the seasoning adheres uniformly.

Preheat your air fryer to 375°F (190°C) for 3 to 5 minutes. Carefully place the seasoned Brussels sprouts into the air fryer basket or tray. Arrange the sprouts in a single layer as much as possible; do not overcrowd. Cook in two batches if necessary to maintain proper airflow.

Set the air fryer timer for 12 minutes and begin cooking.

When the timer reaches the halfway mark (after 6 minutes of cooking), pause the air fryer, pull out the basket, and shake the sprouts vigorously to turn and redistribute them. Return the basket and resume cooking.

Check the sprouts around the 10-minute mark. For extra dark and crispy leaves, increase the temperature to 400°F (200°C) for the last 2 to 3 minutes of cooking. The sprouts are finished when the outer leaves are deeply browned, slightly charred, and the center is tender (total cook time: 12 to 15 minutes).

Carefully transfer the crispy air-fried Brussels sprouts to a serving platter. If desired, drizzle the warm sprouts with 2 tablespoons of balsamic glaze or sprinkle generously with freshly grated Parmesan cheese immediately before serving. Serve hot as a healthy side dish.