Preheat oven to 325 F.
Season chicken with salt and pepper. Put the cornstarch in a shallow bowl. Beat the eggs in another shallow bowl.
Working in two batches, toss the chicken pieces in cornstarch and then coat with the egg. Set aside on a tray.
Heat the oil over medium-high heat in a large skillet. When oil is hot, again in two batches, brown the chicken, turning it so that all sides are browned. Make sure it’s nice and brown on all sides. Then remove it from the skillet using tongs and place the chicken in a single layer in a 9×13 baking dish. Repeat frying the rest of the chicken.
Whisk together the sauce ingredients (sugar, ketchup, vinegar, soy sauce, garlic powder, sesame seeds) in a small bowl and pour evenly over the chicken. Turn the chicken to ensure each piece is coated.
Bake for 1 hour, turning the chicken every 15 minutes.