Pour the stock into a large saucepan and bring up to the boil.
Add the ginger, chilli, spring onions, Chinese five spice powder, sugar, sweet chilli sauce and soy sauce, reduce the heat and simmer gently for 5 minutes.
Add the mushrooms and noodles and simmer for 3–4 minutes until the noodles are cooked.
Stir in the pak choi and lime juice and check the seasoning.
Simmer for a further 2 minutes.
Ladle into bowls and sprinkle with coriander to serve.
Extracted from Love to Cook by Mary Berry (BBC Books, £26). Photography by Laura Edwards.