Special equipment: a wok
For the sauce: Add the vegetable stock, cornstarch, hoisin sauce, ketchup, soy sauce, vinegar and chili sauce to a medium bowl and stir to combine.
For the chicken: Place the chicken in a bowl and sprinkle with salt and pepper. Add the potato flour or cornstarch and mix well to coat the chicken pieces.
Heat a wok over high heat until it starts to smoke and then add the peanut oil. Add the Sichuan peppercorns and dried chiles and fry for a few seconds, then add the chicken pieces and stir-fry for 2 minutes. As the chicken begins to turn opaque, add the rice wine or dry sherry. Cook for an additional 2 minutes, then pour in the sauce.
Bring the mixture to a boil, add the red pepper and cook until the meat is cooked through and the sauce has thickened and become slightly sticky in consistency, another 2 minutes. Add the scallions and cook for 1 minute. Toss in the cashews, then transfer to a serving plate and serve immediately.