In a mixing bowl, whisk together gochujang, soy sauce, honey, sesame oil, garlic, ginger, rice vinegar, sesame seeds, and red pepper flakes. Stir in chopped green onions.
Marinate the chicken
Place the chicken in a ziplock bag or shallow dish and pour the marinade over it. Ensure each piece is well-coated. Marinate in the refrigerator for at least 1 hour (or overnight for deeper flavor).
Preheat the grill
Heat a grill or stovetop grill pan to medium-high heat. Lightly oil the grates to prevent sticking.
Grill the chicken
Remove the chicken from the marinade, letting excess drip off. Grill each piece for about 4-5 minutes per side until fully cooked and slightly charred. The internal temperature should reach 165°F (75°C).
Rest and garnish
Let the chicken rest for 5 minutes before slicing. Sprinkle with toasted sesame seeds and green onions.
Serve
Enjoy with steamed rice, lettuce wraps, or alongside kimchi and pickled vegetables.