Directions

1. Bring the water or stock, fish sauce, lime leaves, lemongrass, galangal, garlic, salt and pepper to a boil in a large pot over medium flame. Reduce heat to low and simmer for 15-20 minutes. Remove from heat and set aside for another 10 minutes to steep. Strain through a fine-meshed sieve and discard solids.
2. Return the stock to a simmer over medium-low heat. Add the shrimp, scallions and mushrooms and continue to simmer over medium-low heat until shrimp is cooked through, 5-6 minutes.
3. Stir in the lime juice, cilantro and chilies, adjust seasoning and serve.
4. Add the shrimp shells from peeling the shrimp to the simmering stock for extra flavor. Straw mushrooms are usually found canned. You can substitute thinly sliced button mushrooms if you like, or omit the mushrooms altogether. Sliced bamboo shoots can be added if you like. If kaffir lime leaves are unavailable, zest the limes before juicing them and use the zest instead.
5. Tom Kha Kung: Substitute coconut milk for half or all the water or stock. Tom Yum Gai: Substitute thinly sliced chicken for the shrimp. Tom Yum Hed: A vegetarian variation. Eliminate the shrimp and double the amount of mushrooms.