Prep the chicken: In a bowl, mix soy sauce, Shaoxing wine, sesame oil, cornstarch, and white pepper. Add chicken and toss to coat. Marinate 10–20 minutes while you prep the rest.
Make the sauce: In a small bowl, whisk light soy, dark soy, black vinegar, Shaoxing wine, sugar, stock, and cornstarch until smooth.
Set aside.
Prep aromatics and vegetables: Mince garlic and ginger. Separate scallion whites and greens. Cut bell peppers into bite-size pieces.
Lightly crush Sichuan peppercorns with the flat of a knife.
Toast chilies and peppercorns: Heat a large wok or skillet over medium heat. Add 1 tablespoon oil. Toss in dried chilies and Sichuan peppercorns.
Stir 30–45 seconds until fragrant and slightly darkened. Do not burn. Transfer to a plate.
Sear the chicken: Turn heat to high. Add 1–2 tablespoons oil.
Spread chicken in a single layer. Let it sear 60–90 seconds before stirring. Cook 3–4 minutes until mostly cooked with browned edges.
Remove to a plate.
Stir-fry veggies and aromatics: Add a little more oil if needed. Add bell peppers and scallion whites. Stir-fry 1–2 minutes until crisp-tender.
Add garlic and ginger. Stir 20–30 seconds until fragrant.
Combine and sauce: Return chicken, chilies, and peppercorns to the pan. Stir the sauce (cornstarch settles) and pour it in.
Toss quickly over high heat 60–90 seconds until thick, glossy, and clinging to the chicken.
Finish: Stir in peanuts and a drizzle of chili oil if using. Turn off heat and fold in scallion greens.
Serve: Plate immediately over steamed rice. Enjoy while hot and crisp.