Make the sauce: In a medium bowl whisk together hoisin sauce, orange zest, orange juice, soy sauce, sugar, sesame oil, 1 tablespoon cornstarch, and 2 tablespoons water until smooth; set aside.
Prepare the wet batter: In a bowl whisk 1½ cups of the flour (reserve remaining flour), the ice-cold 1 cup water, and 1 large egg until a pancake-batter consistency forms; do not overmix.
Prepare the dry dredge: In a separate bowl combine the remaining 1 cup of flour, 1/4 cup cornstarch, 1 teaspoon salt, and 1/2 teaspoon black pepper.
Heat oil: Pour about 2 inches of vegetable oil into the wok or pot and heat to 350°F (use a thermometer).
Coat the chicken: Working in batches, dip chicken pieces into the wet batter, then dredge in the dry flour mixture to coat; set the coated pieces aside.
Fry the chicken: Fry coated chicken in batches until golden brown and very crispy, then remove with a spider or tongs and drain on paper towels.
Discard oil and wipe wok: Carefully pour out the frying oil and wipe the wok clean with paper towels, then heat 2 tablespoons vegetable oil over high heat.
Stir-fry aromatics: Add minced ginger and garlic to the hot oil and stir-fry for about 30 seconds, stirring constantly until fragrant.
Cook the sauce: Pour in the reserved sauce, stir frequently, bring to a boil, and simmer 2–3 minutes until slightly thickened.
Toss chicken in sauce: Add the fried chicken to the wok and stir to fully coat each piece in the sauce.
Serve: Serve immediately over steamed rice and garnish with chopped scallions if desired.
