Heat the oil in a saucepan, add the chicken and fry for 4–5 minutes, stirring until golden. Add the mushrooms and carrot sticks, then the ginger, chillies, miso, mirin or sherry and soy sauce.
Pour on the water and bring to the boil, stirring. Simmer for 10 minutes.
Add the pak choi, spring onions and chopped coriander and cook for 2–3 minutes until the pak choi has just wilted. Spoon into bowls and serve.