When I was growing up, whenever my family would order from our favorite Chinese restaurant, we'd order the same things: many orders of pot stickers and kung pao chicken, hold the peanuts (because my mom is allergic!). Even as a picky eater, I loved how saucy and flavorful the kung pao chicken was. Every single time we ordered it, my older sister would pick out a dried chile with her fingers, hold it in my face, and try to convince me to eat this "dehydrated carrot." I never fell for it!
Whisk together the cornstarch, 1 tablespoon soy sauce and 1 tablespoon rice vinegar in a medium bowl. Add the chicken, then toss to coat and let marinate at room temperature, 20 minutes.
Combine the hoisin, sugar, remaining 2 tablespoons soy sauce, remaining 2 tablespoons rice vinegar and 2 tablespoons water in a small bowl. Grate the garlic and ginger into the sauce. Stir and set aside.
Heat a wok or large skillet over medium-high heat. Add the oil, then add the chicken. Stir-fry until browned on the outside, 3 to 5 minutes. Add the chiles, green beans, red pepper, scallions whites, Sichuan peppercorn powder and peanuts. Stir-fry until fragrant and the veggies are crisp-tender, 3 to 5 minutes. Add the sauce and simmer until thickened slightly and the chicken is completely cooked through, 2 to 4 minutes. Garnish with the scallion greens and additional peanuts. Serve with the rice.