Step 2

Pour the stock into a medium pan and bring it to a rolling boil. Add the aromatics — lemongrass, galangal, cilantro roots, lime leaves — and hold at a simmer for two minutes.

Step 3

Slide in the shrimp and cook only until they curl and turn opaque. In a broth this thin they go rubbery quickly, so watch them.

Step 4

Season with the fish sauce, sliced chilies and lime juice. It should land sour first, then hot, then salty.

Step 5

Taste and correct with more lime or fish sauce before ladling into bowls. Scatter the cilantro leaves over at the last moment.