Marinate the Chicken: In a mixing bowl, combine the chicken pieces with the light soy sauce, cornflour, and sesame oil. Use your hands to massage the marinade into the meat until every piece is coated. Let it rest for 15 minutes. The chicken will feel slightly tacky and look glossy.

Prepare Your Sauce and Aromatics: In a small bowl, stir together the chicken stock substitute, dark soy sauce, rice vinegar, sugar, and ground Sichuan peppercorns until the sugar dissolves. Have your minced garlic, julienned ginger, snipped dried chillies, and fresh chilli rings ready in a small bowl. This mise en place is crucial because the cooking happens fast.

Blanch the Green Beans: Bring a small pot of salted water to a rolling boil. Add the green beans and blanch for exactly 2 minutes. You will see them turn a vibrant, bright green. Immediately drain and plunge them into a bowl of ice water to stop the cooking. This step ensures they stay crisp-tender in the stir-fry, not mushy.

Get Your Pan Screaming Hot: Place a large wok or a heavy-bottomed frying pan over the highest heat your hob can manage. Add 1 tablespoon of vegetable oil and swirl to coat. The oil should shimmer and almost smoke within 30 seconds. This is the key to the wok hei.

Sear the Chicken: Add the marinated chicken pieces in a single layer. Do not stir for the first 90 seconds. You want to hear a loud, aggressive sizzle. When the bottom is a deep golden brown (you'll see the edges crisping), stir-fry for another 2-3 minutes until the chicken is cooked through and no longer pink inside. The chicken should feel firm to the touch and have a lovely browned crust. Remove the chicken to a plate and set aside.

Cook the Aromatics and Vegetables: Add the remaining 2 tablespoons of oil to the hot pan. Immediately add the garlic, ginger, dried chillies, and fresh chillies. Stir-fry for about 20-30 seconds until the garlic is fragrant and just beginning to turn golden. You'll smell a punchy, spicy aroma. Add the blanched green beans and diced bell pepper. Stir-fry for 2 minutes; the peppers should still have a bit of crunch and the beans should have a slight char.

Combine and Finish: Return the seared chicken to the pan. Pour the prepared sauce over everything. Add the chilli oil. Stir-fry vigorously for another 60-90 seconds, tossing everything together until the sauce thickens, coats every piece of chicken and vegetable, and looks dark, glossy, and rich. The sauce should cling to the ingredients rather than pool at the bottom of the pan.

Serve Immediately: Remove the pan from the heat. Garnish generously with sliced spring onions. Serve immediately over a bed of steaming jasmine rice.