Prepare the chicken coating: In a large bowl, combine cornstarch, flour, salt, and pepper. In another bowl, beat the eggs. Dip each chicken piece into the egg mixture, then coat evenly with the flour-cornstarch blend. Shake off any excess coating so the pieces don’t clump together while frying.
Fry the chicken: Heat about 2 inches of vegetable oil in a deep skillet or pot over medium-high heat (around 350°F / 175°C). Once the oil is hot, carefully add the chicken in batches. Fry until golden brown and crispy, about 4–6 minutes per batch. Transfer to a wire rack or paper towel-lined plate to drain excess oil.
Make the orange sauce: In a saucepan, combine orange juice, sugar, vinegar, soy sauce, garlic, ginger, and orange zest. Stir well and bring to a gentle simmer over medium heat. Once it starts to bubble, add the cornstarch-water mixture and continue stirring until the sauce thickens and becomes glossy, about 3–4 minutes. Taste and adjust sweetness or tanginess if needed. If you like a bit of spice, stir in some chili flakes.
Combine chicken and sauce: Place the fried chicken pieces in a large mixing bowl or wok. Pour the hot orange sauce over the chicken and toss gently until each piece is evenly coated. The chicken should glisten with that signature orange glaze — sticky, shiny, and full of citrus aroma.
Serve and enjoy: Serve your Costco-style orange chicken over steamed white rice or fried rice. Garnish with sliced green onions and a sprinkle of sesame seeds for a restaurant-style presentation.
