Notes: The rice noodles that I used were 1/4-inch wide. If yours are wider, they may take longer to cook. Though the instructions say to par-boil, I like my noodles firm, so I usually just add them directly to the dish to cook. Other noodles, such as rice vermicelli, can be substituted. You can also briefly cook the noodles separately, and then divide into bowls and ladle the soup over the top. I used 5 long green chilies (unseeded) to get the perfect amount of heat, but your chilies may have a different level of hotness. Start with 3 and then increase if necessary. Thai bird chilies can also be used.
- 12 ounces boneless, skinless, chicken breast, sliced into 1/4-inch strips
- 1 to 2 tablespoons fish sauce, divided
- 6 ounces rice noodles (see note)
- 6 cups homemade or store-bought low-sodium chicken stock
- 2 stalks lemongrass (white parts only), minced
- 3 to 5 long green chilies (see note)
- 2 to 3 tablespoons lime juice from 3 large limes
- 1/4 teaspoon sugar
- 8 ounces white mushrooms, trimmed and sliced into 1/2-inch slices
- 1 large bunch cilantro, roots trimmed, rinsed
- 1 medium onion, sliced into thin rings
Toss chicken with 2 teaspoons fish sauce in a small bowl; set aside. Cover rice noodles with cool water; set aside.
Heat chicken broth, lemongrass, and chilies in large pot over medium heat to simmer. Simmer 5 minutes. Add 1 tablespoon fish sauce, 2 tablespoons lime juice, sugar, and mushrooms. Simmer until mushrooms are half-cooked, about 2 minutes.
Cut stems from cilantro and add to pot. Season to taste with lime juice, chilies, fish sauce, sugar. Add chicken and gently simmer until just cooked through, about one minute. Drain noodles and add to soup. Simmer briefly until cooked through but firm. Garnish with sliced onion and handfuls of cilantro leaves.