Prepare the Chicken: Season the chicken with salt, black pepper, garlic powder, and onion powder.
Make the Batter: In a bowl, mix cornstarch, flour, egg, and cold water to form a smooth batter.
Fry the Chicken: Heat oil in a deep pan to 350°F (175°C). Dip the chicken pieces in the batter, then fry in batches for 4-5 minutes until golden. Remove, drain, and let rest for 5 minutes. Double-fry for another 2-3 minutes for extra crispiness.
Make the Sauce: In a pan, combine gochujang, soy sauce, honey, brown sugar, rice vinegar, garlic, ginger, sesame oil, and red pepper flakes. Simmer for 2-3 minutes until slightly thickened.
Coat the Chicken: Toss the crispy chicken pieces in the sauce until well coated.
Serve: Garnish with green onions and sesame seeds. Enjoy on its own or with rice!