Stir in the mushrooms, chicken stock, and coconut milk. Bring to the boil, then simmer for 20 minutes.
10 chestnut mushrooms, 500 ml (2 cups + 2 tbsp) chicken stock, 240 ml (1 cup) full-fat coconut milk
Whilst the soup is simmering, cook the noodles as per the pack instructions (usually this means cook in boiling water for 4 minutes). Drain the noodles and run under cold water to stop the cooking process. Drain again when the noodles are cold.
150 g (5.3 oz) dried medium egg noodles
When the soup has simmered for 20 minutes, add in half the lime juice and a pinch of salt and pepper. Taste, then add more lime juice and seasoning if needed.
1 lime, pinch salt and pepper
Add in the spring onions and allow to cook for a further minute or two to soften slightly, then stir in the cooked noodles and heat for 1-2 minutes to heat them through.
1 small bunch spring onions (scallions)
If you would like the soup to be a little thicker, you can mix the 2 tbsp of cornflour with 6 tbsp of cold water, and add a splash at a time to the soup, whilst stirring to thicken.
2 tbsp cornflour
Turn off the heat and divide the soup between four bowls. I find it easier to use tongs to place the noodles into the bowls first, then ladle the rest of the soup on top.
Sprinkle with the sliced chillies and chilli flakes before serving.