Cut the chicken into evenly sized bite-sized pieces and pat dry with a paper towel.
Mix garlic, ginger, soy sauce, and black pepper in a bowl, add the chicken, and toss to coat. Marinate for 15 to 20 minutes.
Lightly coat the marinated chicken with cornstarch and whole-wheat flour if using.
Preheat the oven or air fryer, spray the chicken lightly with olive oil, and cook in a single layer, turning halfway, until golden and fully cooked.
In a small pan over low heat, combine gochujang, honey, soy sauce, rice vinegar, garlic, and sesame oil, and simmer gently until slightly thickened.
Toss the cooked chicken in the warm sauce until evenly coated.
Garnish with sliced green onions and sesame seeds before serving.