Set a large saucepan over a medium heat and pour in the stock. Finely chop the coriander stalks and add to the stock with most of the chilli. Bring to the boil and add 200ml water. Once boiled, reduce the heat and simmer for 5-10 mins to infuse the coriander and chilli.
Add the soy sauce and a grinding of black pepper, then the mushrooms, pak choi, chicken and noodles. Simmer for 2 mins until the noodles soften, before adding the bamboo shoots.
Serve in deep bowls topped with coriander leaves and the remaining chilli slices.