Begin by cutting the chicken breasts into 1-inch cubes and place them in a mixing bowl.
In a separate bowl, whisk together the honey, soy sauce, minced garlic, grated ginger, sesame oil, rice vinegar, black pepper, and red pepper flakes (if using).
Pour the marinade over the chicken cubes, making sure they are well coated. Cover the bowl with plastic wrap and let it marinate in the refrigerator for at least 30 minutes. For even better flavor, marinate for up to 2 hours.
Preheat your grill or grill pan over medium-high heat.
Thread the marinated chicken onto the skewers, leaving a little space between pieces for even cooking.
Once the grill is hot, place the skewers on it and cook for about 6-8 minutes on each side, or until the chicken is cooked through and has a nice char. The internal temperature should reach 165°F (75°C).
Remove the skewers from the grill and let them rest for a few minutes.
Before serving, sprinkle sesame seeds and chopped green onion over the skewers for added flavor and garnish.