Combine all ingredients for the chicken in a shallow bowl; cover and marinate for 10 minutes.
Whisk sauce ingredients together until sugar dissolves; set aside.
Heat a large skillet, pan or wok over high heat.
Add 2 tablespoons of cooking oil, allow to heat up, then add marinated chicken.
Fry chicken for 3 to 4 minutes while occasionally stirring, until edges are browned.
Remove from heat and set aside.
Add remaining cooking oil into the same pan/wok.
Stir in garlic, ginger, chili diced peppers (capsicums) and Sichuan peppercorns and stir fry for 1 minute.
Give the prepared sauce a mix, then pour it into the pan and bring it to a boil while stirring.
Once it begins to thicken slightly, add chicken back into the pan/wok and mix all of the ingredients through the sauce until the chicken is evenly coated and sauce has thickened, (about 2 minutes).
Stir in green onions, peanuts and sesame oil. Toss well and continue to cook for a further 2 minutes to infuse all of the flavours together.
Serve immediately with steamed/cooked rice or fried rice.