Cut the chicken as evenly as possible into 1cm strips and then cut these into small cubes. Place in a small bowl and mix in the marinade ingredients.
Peel and thinly slice the garlic and ginger, and chop the scallions into chunks as long as their diameter (to match the chicken cubes). Snip the chiles in half or into 5cm sections. Wearing rubber gloves, discard as many seeds as possible.
Combine the sauce ingredients in a small bowl — if you dip your finger in, you can taste the sweet-sour base of the gong bao flavor.
Season the wok, then add two tablespoons of oil and heat over a high flame. When the oil is hot but not yet smoking, add the chiles and Sichuan pepper and stir-fry briefly until they are crisp and the oil is spicy and fragrant. Take care not to burn the spices (you can remove the wok from the heat if necessary to prevent overheating).
Quickly add the chicken and fry over a high flame, stirring constantly. As soon as the chicken cubes have separated, add the ginger, garlic, and scallions and continue to stir-fry for a few minutes until they are fragrant and the meat is cooked through (test one of the larger pieces to make sure).
Give the sauce a stir and add it to the wok, continuing to stir and toss. As soon as the sauce has become thick and shiny, add the peanuts, stir them in, and serve.
VARIATIONS: The same dish can be made with cubes of pork, shrimp, or prawns. Cashew nuts can be used instead of peanuts - although peanuts are more traditional.