Cut the chicken into evenly sized bite-sized pieces and season with salt, pepper, and garlic powder.
Whisk the egg in a bowl.
Combine cornstarch and flour in a separate bowl.
Dip each chicken piece into the egg, then coat thoroughly in the cornstarch mixture.
Heat oil to approximately 350°F (175°C).
Fry the chicken in batches for about 4–6 minutes, or until golden brown and cooked through.
In a saucepan, combine orange juice, orange zest, soy sauce, brown sugar, rice vinegar, honey, garlic, ginger, and red pepper flakes.
Bring the sauce to a gentle simmer.
Mix cornstarch with cold water and whisk the slurry into the sauce.
Cook for 1–2 minutes until glossy and thickened.
Remove from heat and stir in sesame oil if desired.
Toss the freshly cooked chicken with the warm orange sauce.
Garnish with sesame seeds and sliced green onions.
Serve immediately with steamed rice or your favorite side dishes.