Thai Chicken Soup

I love Asian food, especially southeast Asian (things like Thai and Vietnamese). There just seems to be a near perfect balance of sweet, sour, spicy and savory in most of the dishes. All with a wide variety of flavors and textures. It's just amazing stuff. This recipe is one of my favorites, it's a coconut based Thai soup that I've adapted from an America's Test Kitchen recipe.

Thai Chicken Soup:
serves 4

Ingredients-
1 tsp. vegetable oil
3 stalks lemon grass, tough outer leaves removed, bottom 5 inches halved lengthwise and sliced thin crosswise (other than at the Asian market, the only places I've found fresh lemon grass around here is at the Sunflower Market and some Whole Foods stores)
3 large shallots, chopped
8 sprigs fresh cilantro leaves, coarsely chopped
3 TB fish sauce (look in the Asian section of the supermarket)
4 cups low-sodium chicken broth
2 (14oz) cans coconut milk, well-shaken (you can substitute light coconut milk if you want it lower fat)
1 TB sugar
1/2 lb white mushrooms, cleaned, stems trimmed, cut into 1/4-inch slices
1 lb boneless, skinless chicken breasts , halved lengthwise and sliced on bias into 1/8-inch-thick pieces
3 TB fresh lime juice from 2 to 3 limes
2 tsp. red curry paste (Thai)
Garnish
1/2 cup fresh cilantro leaves
2 serrano chiles, sliced thin
2 scallions , sliced thin
1 lime, cut into wedges
Thai basil (optional)

Directions-
1. Heat oil in large saucepan over medium heat, adding lemon grass, shallots, cilantro, and 1 TB fish sauce when it's just starting to shimmer. Cook, stirring frequently until just barely softened (2 to 5 minutes). Don't let the vegetables brown!
2. 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).
3. Pour broth through fine-mesh strainer and discard solids in strainer. Rinse saucepan and return broth mixture to pan (I think this step is fairly optional, it will look prettier if you do it, but sometimes I don't)
4. 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).
5. Add chicken and cook, stirring constantly, until no longer pink (1 to 3 minutes). Remove soup from heat.
6. Combine lime juice, curry paste, and remaining 2 tablespoons fish sauce in small bowl; stir into soup.
7. Ladle soup into bowls, serve with garnishes of cilantro, chiles, scallions, lime and Thai basil (I serve them on the side and let people garnish for themselves, it's easier, more fun and more authentic).

If you want it to be more substantial then serve it over cooked noodles (I just use Ramen without any flavouring) or jasmine rice (about 3 cups worth).