1. Marinade Sauce:

Place ingredients in a jug and mix well until honey is completely dissolved.
Reserve 1/4 cup for basting, refrigerate.
Reserve 2/3 cup for serving sauce, refrigerate.
2. Marinade Chicken:

Pour remaining marinade over chicken in a container. Coat chicken thoroughly.
Cover and refrigerate for 3 to 48 hours (minimum 3 hrs).
3. Serving Sauce (Makes 1 cup):

Place reserved sauce in a small saucepan.
Mix cornflour and water, then add into saucepan.
Simmer over medium heat for 5 minutes, stirring regularly, until it thickens to a syrupy consistency. Set aside and keep warm. If it gets too thick, just add a bit more water.
4. Cook:

Brush BBQ plate or grills with oil and heat to medium-high. Or heat oil in a large skillet over medium-high heat.
For thighs: Cook the first side for 2 minutes, then flip and dab with reserved basting sauce. Cook for 2 minutes, flip and baste. Then flip/baste every 1 minute for a total cook time of ~10 minutes or until a thermometer reads 75°C/165°F.
For breast: Cook the first side for 2 minutes, flip, and baste. Cook for 2 minutes, then flip and baste every 45 seconds or so for a total cook time of ~8 minutes (internal temp 66°C / 151°F).
5. Rest:

Transfer to a serving plate, cover loosely with foil, and rest for 5 minutes.
6. Serve:

Serve chicken garnished with sesame seeds and green onion, with sauce on the side so people can help themselves. Enjoy your delicious Honey Soy Chicken!