In a small bowl, whisk together 2 tablespoons soy sauce, Shaoxing wine, and the cornstarch until smooth. Add the chicken pieces, and toss to coat. Let them sit while you prep the other ingredients for about 10 minutes.

Heat a large skillet or wok over medium-high heat. Add 1 tablespoon of oil and swirl to coat. Add the marinated chicken in a single layer, allowing it to sear without stirring for about 1–2 minutes, so it develops a light crust. Stir-fry until the chicken is just cooked through, then transfer to a plate.

In the same pan, add the remaining 1 tablespoon oil. Add garlic and ginger, cooking for about 30 seconds until fragrant but not burnt. If you like extra heat, sprinkle in red chili flakes or drizzle chili sauce now.

Return the chicken to the pan. Stir in the remaining 2 tablespoons soy sauce, rice vinegar, sugar, and hoisin if using. Toss to coat evenly and let the sauce bubble for about a minute to thicken slightly.

Toss in the roasted peanuts and most of the scallions (reserve a few to garnish). Stir quickly, then finish with a quick burst of heat—just enough to coat everything and warm the peanuts through.

Remove from heat. Taste and adjust with a splash more soy sauce or a pinch of salt if needed. Garnish with the remaining scallions and a final pinch of chili if you want it spicier.