Marinate the chicken: toss the chicken with 1 tablespoon light soy sauce, 1 teaspoon Shaoxing wine, 2 teaspoons cornstarch, and 1 teaspoon oil until lightly coated. Set aside for 10 minutes.
Mix the sauce: stir together the remaining 2 tablespoons light soy sauce, remaining Shaoxing wine, sugar, dark soy sauce if using, cracked black pepper, and chicken stock. Mix the remaining 1 teaspoon cornstarch with 1 tablespoon cold water for the slurry.
Sear the chicken: heat a wok over high heat until it just starts to smoke. Add 1 tablespoon oil, spread the chicken in a single layer, and let it sit 1 minute to brown. Stir-fry 2 to 3 minutes until cooked through and golden. Transfer to a plate.
Cook the vegetables: return the wok to high heat with the remaining 1 tablespoon oil. Stir-fry the onion and bell peppers 1 1/2 to 2 minutes until edges char slightly but peppers stay crisp. Add garlic and ginger and stir 20 seconds until fragrant.
Sauce and finish: return the chicken and juices to the wok. Pour in the pepper sauce and toss 30 seconds. Stir the slurry, drizzle it in, and toss 20 to 30 seconds until glossy and coating everything. Fold in the scallions and remove from heat.
Serve right away: spoon over hot jasmine rice and serve immediately.