Blend the paste ingredients in a food processor until smooth.
Heat olive oil in a large saucepan and fry the paste for 2-3 minutes.
Stir in the coconut milk and fish sauce.
Pour in 1 liter of boiling water and add the stock cube.
Add the prawns and cook in the broth until pink and opaque.
Add mushrooms and sugar snap peas and cook for 2-3 minutes.
Cook the soba noodles in boiling water, then drain.
Add lime juice to the soup and season with salt and pepper.
Divide noodles into four bowls and ladle the soup over them.
Garnish with basil, shiso cress, coriander, chilli, and extra lime juice.