How to Make It
In a medium bowl, toss the chicken with the fish sauce.
In a medium saucepan, combine the stock with the chili paste, sugar, lime leaves and lemongrass and bring to a boil over moderately high heat. Stir in the coconut milk and simmer for 5 minutes.
Add the chicken and fish sauce to the saucepan along with the shiitakes and simmer, stirring occasionally, until the chicken is cooked through and the mushrooms are tender, about 5 minutes. Remove from the heat and discard the lime leaves. Stir in the lime juice and chiles and season with salt. Ladle the soup into bowls. Sprinkle the soup with the cilantro and serve with lime wedges and sliced chiles.
Nam prik pao is a sweet and spicy Thai condiment. It's available at Asian markets and online at kalustyans.com.