Slice the chicken thighs into thin strips then combine in a bowl with the rest of the marinade. Leave to marinate as you prep everything else.
Whisk the 'Sauce' ingredients except the stock in a small bowl. Once the cornflour has blended into the sauce, whisk in the stock.
Cook the noodles in boiling water until al dente (typically a minute off the packet instruction). Drain and rinse in cold water, then leave in the colander until needed.
Heat 2 tbsp oil in a large wok over high heat. Once you see wisps of smoke, add the chicken and immediately use a wooden spoon to separate the pieces so they don't stick. Fry until the strips are golden and cooked through the centre (approx 3 minutes) then remove and place on a plate to one side, leaving the excess oil behind.
Add the onion and stir fry for 1-2 minutes until it softens and just begins to colour, then add the cabbage, carrot and white part of the spring onion and fry for another 2 minutes, or until they soften/wilt.
Give the noodles a final shake in the colander to discard excess water, then add them to the wok and immediately pour in the sauce (give it a quick whisk before pouring it in). Toss to coat the noodles in the sauce, then toss in the beansprouts, remaining spring onion and chicken (alongside the resting juices). Toss and shake the wok until all of the sauce is soaked up and everything is evenly distributed (check for pooling underneath the noodles). The noodles shouldn't be watery at all, just coated in a very light glossy sauce.
Serve up and enjoy!