. In a large pot, bring the lemongrass, lime leaves, galangal or ginger, and water to a boil and then lower the heat to medium. Add the shrimp, chili peppers, and nam prik pao and simmer just until the shrimp is cooked through.
Reduce the heat to medium-low. Add the mushrooms, fish sauce and lime juice. Ladle the soup into bowls, garnish with cilantro, drops of coconut milk and serve.