Marinate chicken: combine chicken pieces with salt, sugar, soy sauce, rice wine, and cornstarch; let rest 10 minutes.
Heat oil in a wok over medium-high heat; fry dried chilies and Sichuan peppercorns until fragrant, then remove and reserve.
Increase heat to high and stir-fry the marinated chicken until crisp and cooked through, then remove and reserve.
Add garlic, ginger, and green onion to the wok; stir-fry until aromatic.
Return chicken, chilies, and peppercorns to the wok; toss quickly to combine and heat through, then serve immediately.