Prep the chicken. Pat the chicken dry with paper towels. Season with salt, pepper, garlic powder, and ginger. Let it sit for 10–15 minutes while you heat the oil.
Heat the oil. Fill a heavy pot with 2–3 inches of oil and heat to 325°F (165°C).
Keep a thermometer handy to maintain the temperature.
Coat the chicken. In a bowl, whisk potato starch and flour. If using eggs, dip the chicken in egg first, then toss in the starch mixture until well coated. Shake off excess.
First fry. Fry in batches without crowding.
Cook each batch for 5–7 minutes for wings or small pieces, until pale golden and cooked through. Transfer to a wire rack to drain. Let the oil return to temperature between batches.
Make the sauce. In a small saucepan over low heat, combine gochujang, soy sauce, honey, rice vinegar, garlic, sesame oil, gochugaru (if using), and water.
Simmer for 2–3 minutes, stirring, until slightly thickened and glossy. Turn off the heat.
Second fry. Increase oil to 350–375°F (175–190°C). Fry the chicken again for 2–3 minutes until deep golden and super crisp.
Drain on the rack.
Sauce it up. Transfer the chicken to a large bowl. Spoon sauce over the chicken and toss until coated. Use as much or as little as you like.
Sprinkle with sesame seeds and scallions.
Serve. Enjoy right away with pickled radish, a simple slaw, or steamed rice.