Marinate the chicken: In a medium bowl, combine the chicken cubes with 2 tablespoons light soy sauce, 1 tablespoon cornflour, and 1 teaspoon sesame oil. Stir until each piece is evenly coated. The chicken should look glossy and feel slightly sticky. Set aside for 15 minutes while you prepare the other ingredients.

Prepare the sauce: In a small bowl, whisk together the Chinese black vinegar, 1 tablespoon light soy sauce, dark soy sauce, sugar, 1 teaspoon cornflour, and chicken stock. The mixture will be a deep, dark brown. Ensure the cornflour is completely dissolved—no white specks remaining.

Toast the aromatics: Heat a large frying pan or wok over medium-high heat until a drop of water sizzles and evaporates instantly. Add 1 tablespoon of vegetable oil and swirl to coat. Add the dried chillies and Sichuan peppercorns. Stir-fry for about 30 seconds until the chillies darken slightly and release a smoky, almost woody aroma. The kitchen will smell intensely fragrant. Remove the chillies and peppercorns from the pan and set aside.

Cook the chicken: Increase the heat to high and add the remaining 2 tablespoons of oil. The oil should shimmer. Carefully add the marinated chicken in a single layer—do not overcrowd. Let it sear undisturbed for 1 minute until the bottom turns a deep golden brown. You'll hear a satisfying sizzle. Stir-fry for another 2-3 minutes until the chicken is cooked through and no longer pink inside. The pieces should feel firm to the touch.

Add aromatics: Reduce the heat to medium. Add the sliced garlic and julienned ginger to the pan. Stir-fry for about 30 seconds until they become fragrant—the smell will turn sweet and pungent. Add the white parts of the spring onion and cook for another 30 seconds, just until they soften.

Combine sauce and nuts: Return the toasted chillies and Sichuan peppercorns to the pan. Pour the prepared sauce over the chicken. Stir immediately and continuously. Within 30-45 seconds, the sauce will thicken and turn glossy, coating every piece. You'll see it bubble and cling to the chicken. Add the roasted peanuts and toss to combine.

Finish and serve: Sprinkle the green parts of the spring onion over the top. Give everything one final stir, then remove from the heat. The chicken should glisten with a rich, dark sauce, and the peanuts should be visible among the chillies. Serve immediately over steamed rice.