Make the Batter:
In a large bowl, whisk flour, cornstarch, baking powder, salt, and white pepper. Create a well and add water, egg, and 2 tablespoons vegetable oil. Whisk until smooth. Let rest 5 minutes.
Prepare Chicken:
Pat chicken pieces dry completely.
Heat Oil:
Fill a heavy-bottomed pot or pan with 2–3 inches of vegetable oil. Heat to 350°F (175°C).
Coat & Fry:
Dip each chicken piece into the batter, letting excess drip off. Fry in batches (6–8 pieces at a time) for 5–6 minutes, until golden brown and cooked through. Transfer to a wire rack over paper towels to drain.
Make the Sauce:
In a saucepan, combine honey, soy sauce, rice vinegar, sesame oil, ginger, garlic, and red pepper flakes. Bring to a simmer over medium heat. Stir cornstarch slurry and pour in while whisking. Cook 30 seconds until thickened, then remove from heat.
Toss & Serve:
Gently toss crispy chicken with warm sauce until coated. Garnish with sesame seeds and green onions. Serve immediately.