Combine the soy sauce, rice vinegar, sesame oil, grated ginger, minced garlic, brown sugar, and gochujang in a large mixing bowl. Stir well until the sugar is fully dissolved.
Add the chicken to the marinade and toss them until they are thoroughly coated. Cover the bowl and refrigerate for at least 1 hour to allow the chicken to marinate.
In a separate bowl, mix together the all-purpose flour, cornstarch, baking powder, and salt until well combined.
Heat vegetable oil in a deep frying pan or pot to a temperature of 180°C (350°F).
Take the chicken out of the marinade, allowing any excess marinade to drip off. Coat each piece of chicken with the flour mixture, shaking off any excess.
Carefully place the coated chicken into the hot oil, frying them in batches to avoid overcrowding the pan. Fry for approximately 8-10 minutes or until the chicken turns golden brown and crispy. Once done, remove the chicken from the oil and let it drain on a plate lined with paper towels.
Repeat the frying process until all the chicken is cooked.
If desired, garnish the Korean Fried Chicken with sesame seeds and chopped spring onions.
Serve the Korean Fried Chicken hot as an appetizer, or as a main dish with steamed rice and pickled vegetables.