Prepare the broth: Bring the water to a boil in a medium pot. Add the lemongrass, galangal, and kaffir lime leaves. Boil for about 5 minutes to release the flavors.
Add the shrimp and mushrooms: Add the shrimp and mushrooms to the pot. Cook until the shrimp turn pink and are fully cooked, about 3-4 minutes.
Season the soup: Add the Tom Yum paste, fish sauce, lime juice, and sugar to the pot. Stir well to combine.
Adjust the seasoning: Taste the soup and adjust the seasoning as needed. Add more lime juice for sourness, fish sauce for saltiness, or sugar for sweetness.
Add the chilies: Add the bruised Thai chilies for heat. Be careful, as the chilies can be very spicy.
Finish with cilantro: Once the soup is well-seasoned and balanced, turn off the heat. Add the chopped cilantro.
Serve hot: Serve the Tom Yum Goong hot in individual bowls. Enjoy it with steamed rice or as a standalone dish.
This spicy and tangy soup is a classic in Thai cuisine and is sure to delight anyone who enjoys bold flavors. Enjoy!