Use paper towels to pat chicken dry; Place chicken into a large zip top bag or bowl.
To a small bowl, add the marinade ingredients: 1 tablespoon soy sauce,1 tablespoon wine (or sherry), 1 tablespoon cornstarch, and the baking soda. Whisk to combine.
Pour marinade over the chicken pieces. Seal or cover the bag/bowl and chill in the refrigerator for 30 minutes.
Meanwhile, chop the vegetables and gather the seasonings so that everything is prepared before you start cooking.
In a medium bowl, whisk together remaining 1 tablespoon wine/sherry, 3 tablespoons soy sauce, 1 tablespoon sesame oil, sugar, rice vinegar, and cornstarch. Set aside.
After 30 minutes, remove chicken from the marinade, then immediately discard the marinade.
Heat 1-2 tablespoons of vegetable oil in a large skillet or work over medium high heat. Add chicken and cook for 5-7 minutes, stirring to brown on all sides. Ensure that chicken is cooked through (no pink should remain and internal temperature of chicken should be 165°F.) Transfer chicken from the pan onto a plate and set aside. ** You may need to cook chicken in batches so the chicken can cook in a single layer with space between each piece.
Add the remaining tablespoon of sesame oil to the skillet, along with the ginger, garlic, and peppercorns. Saute for 1-2 minutes, until the garlic and ginger are fragrant.
Add the bell peppers, zucchini, scallion (reserve some for garnish), and dried chile peppers. Saute for another 1-2 minutes. The vegetables should be tender-crisp, not soggy.
Add the sauce mixture to the skillet, stirring and cooking until it thickens. Add the chicken and peanuts to the pan and heat all ingredients through, tossing to coat the chicken and vegetables with sauce.
Serve hot, garnished with reserved scallion. Store leftovers in an airtight container in the refrigerator for up to 3 days, or freeze for up to 3 months.
Notes
The chiles and peppercorns add spiciness to this dish. Saute them for longer (or prior to adding vegetables and other ingredients to the pan) to kick up the heat. You can substitute red chile paste or red pepper flakes if you can’t find the peppercorns and/or dried chiles, but their distinctive flavors are a signature part of Kung Pao chicken.Unless you have a well-seasoned wok, I highly recommend using a nonstick skillet for cooking. This will allow you to brown the chicken without the marinade/coating sticking to the skillet. A deep golden brown on the chicken gives it great flavor and a lovely appearance. This is difficult to replicate in a stainless steel skillet or an unseasoned work.