Cut chicken into thin slices and mix it well with soy sauce, sesame oil, baking soda, Shao Xing wine, and corn starch. Set it aside and marinate for 15 minutes.
In a small bowl, combine all the stir fry sauce ingredients, mix it well, and set it aside.
Heat the large wok or pan over medium-high heat, drizzle 2 tbsp of oil and add the marinated chicken slices. Flatten and sear the chicken for 2 minutes then flip and continue stir fry for 1-2 minutes.
Add onions and bell peppers and cook for another 1 minute. Remove everything from the pan and set them aside.
In the remaining pan, drizzle 1 tbsp of oil, saute the garlic and ginger for a few seconds until fragrant. Add fermented black beans and stir fry for a few seconds.
Pour the sauce mixture in and stir it well until the sauce is slightly thickened.
Add the cooked chicken and vegetables back in the pan and combine well with the sauce and stir fry until the sauce is thick and glossy.
Finish with spring onions and toss it well with the rest of the ingredients.
Transfer to serving plate. Serve with plain rice or noodles.