Preheat air fryer to 400 F / 200C.
Mix chicken and cornstarch in a bowl until pieces are coated.
Add chicken into the air fryer basket and cook for 8-10 minutes until cooked through, making sure to shake halfway through cooking. Remove and set aside.
Prepare sauce by combining orange juice, brown sugar, soy sauce, water, vinegar, sesame oil, garlic, ginger and the cornstarch slurry in a saucepan or wok. Let simmer over low medium heat for about 5-7 minutes, until the sauce thickens.
Switch off the heat and add in the cooked chicken, mixing until coated. Remove, garnish as desired, and serve.