Tom Yum Goong (Thai Hot and Sour Shrimp Soup)

Method

1. 1Make the shrimp stock. Peel the shrimp and set the meat aside. Put the heads and shells in a pot with the water. Bring to a boil, pressing the heads with a spoon to extract the orange coral oil. Simmer 10 minutes until the stock turns a rich amber-orange. Strain and discard the shells. Return the stock to the pot.
2. 2Infuse the aromatics. Bash the lemongrass with the back of a knife until it splits and cut it into 5 cm pieces. Tear the lime leaves in half, pulling out the tough center rib, and lightly crush the chillies. Add them to the strained stock with the galangal. Bring to a boil, then simmer 5 minutes. The broth should smell intensely of citrus and lemongrass. The aromatics are left in the soup for presentation — warn guests they are not meant to be eaten.
3. 3Add vegetables. Add the onion, mushrooms, and tomato wedges. Simmer 3 minutes until the mushrooms are just tender and the tomatoes begin to soften.
4. 4Add shrimp and season. Add the peeled shrimp and simmer for 1 to 2 minutes, just until they turn pink and the flesh is opaque all the way through. Overcooked shrimp go rubbery. Add the fish sauce, nam prik pao (if using), and sugar. Stir to dissolve the chilli paste. Taste the broth: it should be intensely savory, slightly sweet, and hot from the chillies. The sourness comes next.
5. 5Add lime juice off the heat and serve. Turn off the heat, then add the lime juice to the pot, or squeeze it into each bowl and ladle the soup over it. Lime juice added while the soup is still on the stove loses the volatile citrus compounds that make the sourness fresh. Taste and adjust with more fish sauce, lime, or sugar, then ladle into bowls. Garnish with fresh cilantro. Serve immediately with jasmine rice.