Ingredients

1teaspoon vegetable oil

3stalks lemon grass , tough outer leaves removed, bottom 5 inches halved lengthwise and sliced thin crosswise

3 large shallots , chopped

8sprigs fresh cilantro leaves , chopped coarse

3tablespoons fish sauce

4cups low-sodium chicken broth

2 (14-ounce) cans coconut milk , well-shaken

1tablespoon sugar

1/2pound white mushrooms , cleaned, stems trimmed, cut into 1/4-inch slices

1pound boneless, skinless chicken breasts , halved lengthwise and sliced on bias into 1/8-inch-thick pieces (see illustration below)

3tablespoons fresh lime juice from 2 to 3 limes

2teaspoons red curry paste (Thai)

Garnish

1/2cup fresh cilantro leaves

2 serrano chiles , sliced thin

2 scallions , sliced thin on bias

1 lime , cut into wedges

Preparation

  1. Heat oil in large saucepan over medium heat until just shimmering. Add lemon grass, shallots, cilantro, and 1 tablespoon fish sauce; cook, stirring frequently, until just softened, 2 to 5 minutes (vegetables should not brown). Stir in chicken broth and 1 can coconut milk; bring to simmer over high heat. Cover, reduce heat to low, and simmer until flavors have blended, 10 minutes. Pour broth through fine-mesh strainer and discard solids in strainer. Rinse saucepan and return broth mixture to pan.

  2. Return pan to medium-high heat. Stir remaining can coconut milk and sugar into broth mixture and bring to simmer. Reduce heat to medium, add mushrooms, and cook until just tender, 2 to 3 minutes. Add chicken and cook, stirring constantly, until no longer pink, 1 to 3 minutes. Remove soup from heat.

  3. Combine lime juice, curry paste, and remaining 2 tablespoons fish sauce in small bowl; stir into soup. Ladle soup into bowls and garnish with cilantro, chiles, and scallions. Serve immediately with lime wedges.