Marinate the Chicken
Toss the chicken pieces with soy sauce and cornstarch in a bowl. Let marinate for 15 minutes while you prepare the other ingredients.
Prepare the Sauce
In a small bowl, whisk together soy sauce, rice vinegar, hoisin sauce, chili garlic sauce, sugar, and chicken broth. Set aside.
Cook the Chicken
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the chicken and cook until golden and fully cooked, about 5-7 minutes. Remove and set aside.
Sauté Aromatics
Add the remaining oil to the skillet. Sauté the minced garlic, ginger, Szechuan peppercorns, and dried chilies (if using) until fragrant, about 1 minute.
Stir-Fry Vegetables
Add the bell peppers and onion to the skillet. Stir-fry for 3-4 minutes until tender-crisp.
Combine and Cook
Return the cooked chicken to the skillet. Pour in the sauce and stir to coat everything evenly. Add the cornstarch slurry and simmer for 2-3 minutes until the sauce thickens.
Serve
Remove from heat and serve hot over steamed rice or noodles.