In a shallow dish, add potato starch, lightly coat each piece of beef and place in a single layer in an air fryer. Spray the beef with cooking oil.
Air fry for 10 mins at 400°F, stirring once at about halfway mark. Cook until the beef is evenly browned and crispy. If using a smaller air fryer, you may need to cook in multiple batches at 10 minutes per batch.
Meanwhile, in a small bowl, combine sauce ingredients and set aside.
add onion and carrots. Cook for 3 minutes until softened.
Add garlic and ginger and cook for 30 seconds, until fragrant. Add the sauce and let simmer for about 3 minutes. In the same bowl, dissolve cornstarch in cool water to make a slurry. Add the slurry to the sauce and cook until the sauce starts to simmer and thicken.
Add the cooked beef until the beef is well covered with the sauce and heated through.
Turn off the heat. Stir in green onion.