Slice chicken breasts into thick slices. Rub the chicken breasts with salt and pepper. Put them in large gallon zip lock bags. I used two bags.
Add marinade evenly to both bags - sesame oil, corn syrup, soy sauce, gochujang sauce, green onions, ginger, garlic, chili flakes, sesame seeds. Close bags and refrigerate for at least 5 hours - 24 hours.
After chicken is done marninating, take it out of the fridge. Heat your grill to medium head and spray the grill with non-stick spray. Grill chicken for 4 minutes per side. The marinade will heat up and char the chicken on the outside. Cook until done inside. Cut one piece in half to see if the chicken is cooked inside.
Remove from heat and let rest while you prepare the toppings. Cut chicken into small pieces to serve. Sprinkle chicken with chopped green onions.
Prepare the toppings, arrange it all on a platter.
Serve!