Preheat air fryer to 400F / 200C.
Mix bite-sized chicken and corn starch in a bowl until the pieces are coated.
Place chicken into the air fryer basket and cook for 9-10 minutes or until cooked through, making sure to shake halfway through cooking. Set aside once done.
While the chicken cooks, prepare your sauce by combining chicken stock, brown sugar, soy sauce, vinegar, tomato sauce, hoisin sauce, sesame oil, garlic and ginger, and cornstarch slurry in a saucepan or wok and let simmer over low to medium heat for about 4-5 minutes until the sauce thickens.
Switch off the heat and add cooked chicken into the sauce and mix until coated.
Remove and serve with rice and steamed or sautéed veggies.