Thai Chicken Soup for Two

1 teaspoon vegetable oil
1 large or 2 small lemongrass stalks, tough outer leaves removed, bottom trimmed, halved lengthwise, and sliced thin crosswise
3 small shallots, diced medium
4-5 whole sprigs fresh cilantro, chopped coarse
5 teaspoons fish sauce
2 cups low-sodium chicken broth
1 (14-ounce) can coconut milk, well shaken
1 tsp sugar
6 oz white mushrooms, cleaned, stems discarded, cut into 1/4-inch slices
1 boneless skinless chicken breast (about 1/2 pound), halved lengthwise and sliced crosswise into 1/8-inch pieces
1-1/2 tablespoons lime juice from 2 limes
1 teaspoon Thai red curry paste

Garnish
1/3 cup rough chopped cilantro
1 serrano or jalapeno chili, sliced very thin
2 scallions, sliced thin on the bias
1 lime, cut into wedges

1. Heat oil in large saucepan over medium heat until just shimmering. Add lemongrass, shallots, cilantro, and 1 tablespoon (3 teaspoons) fish sauce; cook, stirring frequently, until just softened, 2 to 5 minutes (vegetables should not brown). Stir in chicken broth and half the can of coconut milk; bring to simmer over high heat. Cover, reduce heat to low, and simmer until flavors have blended, 10-15 minutes. Pour broth through fine-mesh strainer and discard solids in strainer. Rinse saucepan and return broth to pan.

2. Return pan to medium-high heat. Whisk remaining ½ can coconut milk and sugar into broth 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, about 1 minute. Remove soup from heat.

3. Combine lime juice, red curry paste, and remaining 2 teaspoons fish sauce in small bowl; stir into soup. Ladle into bowl and garnish with cilantro, chilies, and scallions. Serve lime wedges on side.