Cut chicken into 1-inch pieces, pat dry and season with salt and pepper.
Put 1/4 cup cornstarch, egg whisked with 1 tablespoon water, and panko in three bowls.
Coat chicken lightly in cornstarch, then egg, then panko.
Preheat the air fryer to 390°F if recommended. Arrange chicken in one layer and mist with oil.
Cook for 5 minutes. Turn, mist dry patches and cook 4 to 7 minutes more, until at least 165°F.
Simmer orange juice, zest, soy sauce, sugar, vinegar, sesame oil, ginger and garlic for 3 minutes.
Mix remaining 1 tablespoon cornstarch with 2 tablespoons cold water. Whisk into the sauce and simmer 1 to 2 minutes.
Toss only the serving portion of hot chicken with a light layer of sauce. Serve immediately.