In a large bowl, combine the chicken pieces with buttermilk, garlic powder, onion powder, black pepper, and salt. Mix well and let marinate in the refrigerator for at least 1 hour, or up to overnight for best flavor.

In a separate bowl, whisk together the flour, cornstarch, and baking powder.

Remove the chicken from the marinade, allowing excess buttermilk to drip off, and dredge each piece in the flour mixture, coating thoroughly.

In a large, deep skillet or pot, heat about 2 inches of vegetable oil over medium-high heat until it reaches 350°F.

Carefully add the coated chicken pieces in batches, frying for about 5-7 minutes or until golden brown and cooked through.

Use a slotted spoon to transfer the chicken to a paper towel-lined plate to drain excess oil.

In a small saucepan, combine gochujang, honey, soy sauce, rice vinegar, sesame oil, minced garlic, and minced ginger. Cook over medium heat, stirring until the sauce is heated through and slightly thickened, about 3-5 minutes.

Toss the fried chicken in the sauce until well coated. Garnish with sesame seeds and sliced green onions before serving.