Create a dipping station, 1 cup flour on a plate, whisked eggs in a dish, 1 cup flour on a plate.
Dredge chicken pieces in flour, dip in whisked egg, then dredge in flour again. Place chicken on wire rack.
Repeat for all chicken pieces.
Heat vegetable oil in a heavy bottomed skillet over medium-high heat until shimmering.
Add chicken pieces to the hot oil, being careful not to crowd, and cook about 2 minutes, then turn and cook a few minutes more. The finished chicken will be golden brown.
Remove chicken to paper towels.
To a clean skillet or wok, add all sauce ingredients except the cornstarch. Whisk together and cook over medium heat until bubbling.
Meanwhile, whisk enough water into the cornstarch to make a slurry (about 1/2 cup). When well combined, pour slowly into sauce mixture, whisking continuously. Allow to thicken then add cooked chicken in. Gently stir, you don’t want to tear off the coating.
We used a heavy bottom skillet to make the chicken and a wok to make the sauce. When cooking the chicken, you want an even cooking surface, which a wok doesn’t have. You do not need to use a wok at all, a saucepan will work fine for making the sauce. Then simply clean the oil out of the skillet you cooked the chicken in and use it to combine the sauce and chicken.
Both the orange juice and the orange zest are key ingredients. I wouldn't recommend substituting or omitting them. You can use either freshly squeezed orange juice or the bottled variety. Both will work, though I suggest going with the freshly squeezed juice for the most flavor, I promise it makes a difference. 3-4 standard size oranges should yield 1 cup worth of juice.
The brown sugar really helps balance out all the flavors in the sauce. It adds a bit of a caramelized taste. You can substitute with granulated white sugar if desired.
Store leftover orange chicken in an air-tight container kept in the refrigerator for up to 4 days. I would recommend reheating it in the air fryer if you have one, or tossing it over low-medium heat in a skillet with a dash of water to loosen the sauce. You can pop it in the microwave if needed, but the coating on the chicken tends to get soggy when reheated this way.