Marinate chicken with all the ingredients listed under 'chicken marinade' for 30 minutes.
Heat sesame oil in wok or pot over medium high heat.
Stir-fry garlic, ginger, and spring onion until fragrant.
Add chicken to brown both sides.
Add mushrooms to cook for 30 seconds.
Pour in all the ingredients for sauce, and give it a stir.
Bring to boil, cover, and reduce heat to low.
Allow to simmer for 35-45 minutes until chicken is tender and sauce reduced.
Drizzle in cornstarch slurry while stirring to thicken sauce.
Serve garnished with chopped spring onions.