Tom Yum Goong (Hot and Sour Shrimp Soup)

Method

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1. 1Peel the shrimp, remove the heads and pull out the dark vein along the back. Refrigerate the shrimp and keep the shells.
2. 2Put the shells in a pot with the water, bring to a boil and simmer gently for 10 minutes. The liquid should turn slightly pink and smell of shrimp; strain and discard the shells.
3. 3Peel the tough outer layers off the lemongrass, bruise the stalks with the back of a knife and cut into 5 cm pieces. Add the lemongrass, galangal and torn lime leaves to the simmering stock and cook for 5 minutes until very fragrant.
4. 4Add the mushrooms and tomato and simmer 2-3 minutes until the mushrooms soften.
5. 5Add the shrimp and cook for 2 minutes, just until pink and curled; any longer and they turn rubbery.
6. 6Take the pot off the heat. Stir in the fish sauce, lime juice, crushed chilies and the chili paste if using.
7. 7Taste and balance sour, salty and hot, adding a little more lime or fish sauce if needed. Sprinkle with cilantro and serve right away.