In a mixing bowl, combine the 2 lb boneless skinless chicken thighs cut into 1.5-inch pieces pieces with 1 tsp soy sauce, ½ tsp sesame oil, ½ tsp kosher salt, and ¼ tsp black pepper freshly ground. Toss to coat evenly and let marinate for at least 10 minutes while you prepare the batter and sauce.

In a large mixing bowl, whisk together the ¾ cup cornstarch, ¼ cup all-purpose flour, 1 tsp baking powder, and ½ tsp kosher salt. Add the beaten eggs and 3 tbsp water cold, then whisk until a smooth, thick batter forms. It should coat the back of a spoon. Add the marinated 2 lb boneless skinless chicken thighs cut into 1.5-inch pieces and toss until every piece is fully coated.

In a small mixing bowl, whisk together the ¾ cup fresh orange juice from about 3 large oranges, 1 tbsp orange zest finely grated, 1 tsp soy sauce, 3 tbsp granulated sugar, 2 tbsp rice vinegar, 1 tbsp hoisin sauce, ½ tsp sesame oil, and ½ tsp red pepper flakes (if using). Set aside. In a separate tiny mixing bowl, mix the ¾ cup cornstarch and 3 tbsp water cold into a smooth slurry and set aside.

Pour the 4 cups vegetable oil into a large pot or wok and heat over medium-high heat until it reaches 350°F. Set a wire rack over a baking sheet lined with paper towels nearby.

Working in 3–4 batches to avoid crowding, carefully lower the battered 2 lb boneless skinless chicken thighs cut into 1.5-inch pieces pieces into the hot oil using tongs or a slotted spoon. Fry for 3–4 minutes, turning occasionally, until golden brown and cooked through. Transfer to the wire rack and repeat with remaining batches. Maintain oil temperature between batches.

In a wok or large skillet over medium heat, add 1 tbsp of the frying oil (or a fresh tablespoon of vegetable oil). Add the minced cloves garlic minced and grated fresh ginger finely grated and sauté for about 30–45 seconds until fragrant — don't let them brown.

Pour in the orange sauce mixture and bring to a simmer over medium heat, stirring occasionally. Cook for 2–3 minutes until the 3 tbsp granulated sugar is fully dissolved and the sauce begins to reduce slightly.

Give the ¾ cup cornstarch slurry a quick stir, then pour it into the simmering sauce while stirring constantly. Cook for 1–2 more minutes until the sauce thickens to a glossy, syrupy consistency that coats a spoon. Remove from heat.

Add all the fried 2 lb boneless skinless chicken thighs cut into 1.5-inch pieces to the wok with the orange sauce. Toss quickly and gently to coat every piece evenly. Serve immediately over steamed white rice, garnished with sliced stalks green onions thinly sliced and 1 tsp sesame seeds.