Combine all the ingredients for the marinade in a large bowl until well incorporated. Add the chicken and stir to coat. Allow to marinate for at least 10 minutes.
For the stir-fry sauce, combine all the ingredients in a bowl, mixing well. Set aside until required.
Heat the oil in a wok over medium-high heat. Add the chillies and stir-fry for 10 seconds. Then add the garlic, ginger, pale part of the spring onion and Sichuan peppercorns. Stir-fry for 30 seconds. Add the chicken and stir-fry for 3-4 minutes or until the chicken is just cooked and the marinade liquid has evaporated.
Next, add the noodles and the stir-fry sauce and toss until well combined and the sauce has thickened slightly. Toss through the green parts of the spring onion. Remove from heat, divide among serving bowls and sprinkle with the peanuts.
