Put the chicken into a large zipper-lock bag (27cm x 33 cm/10.6 inch x 13 inch) and add the sauce. Seal the bag and vigorously shake the bag and massage the chicken so that the sauce smears well onto the chicken. Marinate it for at least 30 minutes in the fridge. (I marinated mine for 4 hrs. Overnight works well too!)
Preheat an oven at 240 C/ 464 F (on the fan forced setting) for 20 mins. Take the chicken out from the fridge. Lay down some baking paper on the oven tray and line up the chicken. Make sure they are not stacked up on top of each other. Alternatively, you can use an oven safe pot and put the chicken in and the marinade. (This is explained above. They result in slightly different outcomes.)
Put the tray/pot into the oven and bake it at 240 C/ 464 F for 12 mins. Take the tray/pot out and turn the chicken over and put it back into the oven. Bake it a further 12 mins or until the chicken is fully cooked. Garnish with the sesame seeds and green onion. Serve.