Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
     1/2  pound         small fresh shrimp shelled -- (shells reserved)
   2      quarts        chicken stock
   2                    green serrano chilies -- seeded and chopped
   1      teaspoon      salt
                        grated zest of one lime
   4                    kaffir lime leaves
   3                    lemon grass stalks -- cut into
                        -- pieces
     1/2  pound         scallops
   2      tablespoons   fish sauce
   3                    limes -- juice of
   3      tablespoons   fresh -- cilantro, chopped,
                        -- up to 4
   1                    red serrano chili -- seeded
                        slivered
   6                    shiitake mushrooms -- sliced
   2                    green onions -- sliced

Preparation:

Combine shrimp shells with stock, chilies, salt, lime, zest, lime leaves and lemon grass stalks in heavy non-aluminum pot. Bring to a boil, reduce heat, cover and simmer 20 to 20 minutes. Strain. Return liquid to pot and place over medium-high heat and bring to a boil. Add shrimp and scallops and cook 1 minute. Stir in fish sauce and juice of limes. Add chopped cilantro, slivered red chili and shiitake slices, and green onions. Stir and pour into a tureen or ladle into individual bowls.