Combine the marinade ingredients and add the chicken. Refrigerate for at least 1 hour up to 4 hours.
Combine all the sauce ingredients in a bowl and mix well to combine.
Drain the excess marinade from the chicken and heat a wok or large cast iron skillet over high heat. Add the cooking oil.
Add the chicken in 3 separate batches (see notes) and cook for about 3-5 minutes, until browned on the outside and cooked through.
Remove the chicken from the pan and cook the next batches the same. Set the chicken aside and turn the heat down to medium.
Add 1 teaspoon of oil to the pan and add the Sichuan peppercorns, dried chilies and peanuts and fry for 1 minute, tossing regularly.
Add the green onions and chicken back to the pan and cook for 30 seconds.
Add the sauce and toss until everything is coated and sauce has thickened, about 1-2 minutes. Remove from heat and serve immediately with steamed white rice.
Be sure to make the sauce before you start to stir fry.
If you're using whole fresh Sichuan peppercorns, you can either add them whole (perfectly acceptable), or you can use a mortar and pestle to grind them.
Any high smoke point oil will work. I prefer canola or vegetable oil for this kind of cooking, but peanut oil, avocado oil or coconut oil also work well.
The chicken must be cooked in batches to avoid overcrowding the pan. We want the edges of the chicken to caramelize, and crowding the pan will cause the chicken to steam instead of fry.
If the sauce is too thin, stir 1 tablespoon of cornstarch with 1 tablespoon of water. Slowly add the cornstarch slurry to the chicken, stirring constantly, until the desired consistency is reached. The sauce should coat the chicken. Add more or less cornstarch slurry as necessary.
Sprinkle the chicken with additional ground Sichuan peppercorns or this homemade Chili Oil.
If you're using raw peanuts, toast them in the oven for 5-10 minutes on 400F OR saute them over medium in a pan with a teaspoon of oil for about 5 minutes, until the outsides are lightly browned.
Add additional dried chilies for extra spice.
Add vegetables like diced red peppers, onions, green pepper, water chestnuts, zucchini or broccoli. Add the vegetables to the wok after the chicken has cooked and cook for 2-3 minutes until just tender. Remove and continue with the rest of the instructions. Add the vegetables back in with the chicken at the end.