Add the stock to a large saucepan with the chilli sauce, bring to the boil, turn down the heat and simmer for 2 minutes. Meanwhile, heat the oil in a non-stick frying pan, add the pork and cook for 7 minutes, turning once. Add the teriyaki sauce and 3 tablespoons of water, and cook for a further 2 minutes or until the juices run clear. Add the mushrooms, pak choi, pepper, noodles and beansprouts to the chilli broth, cover and simmer for 4 minutes until the noodles and vegetables are tender. Slice the pork thinly. Divide the noodles and vegetables between 2 bowls and ladle over the broth. Top each with the pork strips, chilli and coriander. Serve immediately.