1

Cut roots from coriander about 3cm along the stem. Reserve leaves for later. Wash roots very well to remove dirt and chop finely. Bruise lemongrass using a meat mallet or hit with a rolling pin.

2

Bring stock to the boil in a large saucepan. Add coriander roots, lemongrass, lime leaves, ginger, garlic and fish sauce. Simmer for 10 minutes.

3

Add prawns, mushrooms and spring onions and cook for 2-3 minutes, until prawns have changed colour.

4

Add lime juice and chilli to taste, and serve bowls of soup topped with coriander leaves.