Place Brussels sprouts on large sheet of heavy duty aluminum foil, and wrap loosely around Brussels sprouts to form a packet.
Turn “Temperature” switch to 400°F. Set timer to 15 minutes. Once air-fryer is preheated after 5 minutes, place foil packet in fryer basket and cook until tender.
Transfer Brussels sprouts to rimmed baking sheet. Flatten each Brussels Sprout to 1/2-inch thickness using the bottom of a glass or potato masher
Coat Brussels sprouts in oil, salt and pepper. Working in batches, place Brussels sprouts in an even layer in air fryer. Turn “Temperature” switch to 400°F. Set timer to 12 minutes and cook, flipping halfway through until crisp.
Meanwhile, combine brown sugar, ketchup, vinegar and soy sauce in small bowl.
Top crisp Brussels sprouts with green onions and sesame seeds. Serve with soy sauce mixture and enjoy!