In a medium bowl, whisk together the beaten egg, salt, white pepper, and 1 tablespoon of vegetable oil. Add the chicken cubes and toss until fully submerged.
In a separate shallow dish, combine 1/2 cup cornstarch and 1/4 cup flour. Dredge the egg-coated chicken pieces through the dry mixture until thoroughly and evenly coated.
Heat 2 cups of vegetable oil in a wok or heavy-bottomed Dutch oven to 375°F (190°C).
Fry the chicken in small batches to avoid temperature drops, cooking for 3-4 minutes per batch until the exterior is golden brown and crispy. Remove and drain on a wire cooling rack.
In a clean wok or large skillet, heat 1 tablespoon of vegetable oil over medium-high heat.
Add the minced garlic, ginger, and chili flakes; sauté for approximately 30 seconds until the aromatics are fragrant but not browned.
Pour in the brown sugar, orange juice, distilled vinegar, and soy sauce. Stir constantly until the sugar is fully dissolved and the liquid reaches a simmer.
Slowly whisk in the cornstarch slurry. Continue to cook for 1-2 minutes until the sauce thickens and attains a glossy, syrup-like consistency.
Add the fried chicken pieces to the wok and toss rapidly for 30 seconds to ensure even glazing without losing crispness.
Fold in the orange zest and sesame oil, remove from heat immediately, and serve over steamed white rice.