Put a large pan over a medium heat. Cook the curry paste in the oil for 1 min until it starts to release its aroma. Pour in the stock and coconut milk and bring to the boil. Reduce the heat to a simmer and stir in the noodles. Simmer for 7 mins, then stir in the mushrooms and sugar snaps. Cook for 3 mins more, then add the beansprouts, fish sauce and lime juice. Remove the pan from the heat. Ladle the noodles and soup into bowls, then scatter with spring onions, mint and coriander to serve.