In a medium size bowl, combine the chicken pieces with the marinade ingredients. Cover and marinate refrigerated for about 15 minutes.
Heat some oil in a pan/wok, then gently drop the chicken into the oil and loosen them up immediately with the spatula to prevent the chicken pieces from sticking together. Stir fry the chicken to a light golden brown color. Remove the chicken and place on a dish lined with paper towels to remove excess oil and set to one side.
In the same pan you have taken the chicken out of (if needed add a little more oil) add the garlic, stir quickly. Add the ginger and stir quickly. Turn the heat down to medium, add the sliced shallots/oniond and the crushed Sichuan peppercorns. Stir-fry for about 3 minutes until the shallots turn golden brown.
Add the vegetables and continue stir frying for about 3 minutes, until the veg softens up.
Return the chicken to the pan. Stir quickly with a spatula to combine all the ingredients.
Add the rest of the sauce ingredients and continue cooking for another minute or so, until the sauce thickens.
Taste for spiciness. Add more szechuan pepper or chilli if needed and stir.
Serve immediately with white long grain rice