Hot-and-Sour Shrimp Soup

Ingredients

1. 2 tablespoons vegetable oil
2. 3/4 pound shiitake mushrooms, stemmed, caps sliced 1/4 inch thick
3. Salt and freshly ground pepper
4. 4 Thai chiles, minced
5. 3 stalks of fresh lemongrass, inner bulbs only, thinly sliced
6. 1 pound medium shrimp, shelled and deveined, shells reserved
7. 1 large onion, chopped
8. 1/2 cup thinly sliced fresh ginger
9. 1/4 cup Asian fish sauce
10. 2 quarts chicken stock or canned low-sodium broth
11. 1/4 cup fresh lime juice
12. 1/2 cup small basil leaves

1. In a large, deep skillet, heat 1 tablespoon of the oil. Add the shiitake and season with salt and pepper. Cover and cook over moderate heat, stirring a few times, until tender, 5 minutes. Uncover and cook, stirring, until the shiitake are golden, 3 minutes. Transfer to a plate.
2. Add the remaining 1 tablespoon of oil to the skillet. Add the chiles, lemongrass, shrimp shells, onion and ginger and cook over moderate heat, stirring occasionally, until the onion is softened and golden, about 7 minutes. Add the fish sauce and stock and bring to a boil. Simmer over moderate heat for 10 minutes. Strain the shrimp broth into a large bowl.
3. Return the broth to the skillet; bring to a simmer over moderate heat. Add the shrimp and shiitake and cook until the shrimp are pink and curled, 1 minute. Add the lime juice and season with salt and pepper. Ladle the soup into bowls, garnish with the basil leaves and serve.