Galangal, Chicken and Coconut Soup

My mom is visiting so I wanted to cook for her Thai food. I found this soup recipe from cookbook called The food and cooking of Thailand. She loved it:)

Ingredients:
  4 lemon grass stalks, roots trimmed
  2 14-ounce cans coconut milk
   2 cups chicken stock

   1 (l-inch) piece fresh galangal, peeled and thinly sliced
   10 black peppercorns, crushed
   10 kaffir lime leaves, torn (divided use)
    8 ounces skinless, boneless chicken breast portions, cut into thin strips
   1 cup white mushrooms, halved if large
    3 to 4 baby corn cobs, quartered lengthways (optional)
    1/4 cup fresh lime juice
    3 tablespoons Thai fish sauce
    Salt to taste
    2 fresh red Thai chiles, chopped
    1 green onion, chopped
    2 tablespoons chopped fresh cilantro

Instructions:
Cut off the lower 2 inches from each lemon grass stalk and chop it finely. Bruise the remaining pieces of stalk with the flat edge of a large knife. In a large pan over medium heat, bring the coconut milk and chicken stock to boil in a large pan. Add the chopped and bruised lemon grass, galangal, peppercorns and half the kaffir lime leaves; reduce the heat to low and simmer gently for 10 minutes. Strain the soup into a clean pan.
Return the soup to a simmer over medium heat, then stir in the chicken, mushrooms and corn. Simmer gently, stirring occasionally, until the chicken is cooked, about 5 minutes.
Stir in the lime juice and fish sauce, then add the remaining lime leaves. Season with salt to taste. Ladle into warm bowls and serve garnished with chopped chiles, green onions and cilantro.