Thai Yum Yum Soup!

Thai lemon grass soup is one of my favorite things!  It's called "Tom Yum" soup, but I call it "Yum Yum" soup.  Here is the recipe I use:

Tom Yum Soup

Ingredients:
2 pounds raw shrimp
1 Tablespoon oil (sesame works well)
8 cups hot water
1 1/2 teaspoon salt
2 stalks lemon grass (or 4 strips lemon rind, thinly peeled)
4 lemon or other citrus leaves (if you can find them)
2 or 3 fresh whole chilies
1 Tablespoon fish sauce (You buy it bottled.  Sometimes, I leave this ingredient out and it still tastes delicious.)
2 Tablespoons lemon juice, or to taste
1 fresh chili, seeded and sliced
2 Tablespoons chopped cilantro
4 green onions, chopped
sliced mushrooms (1 package)

Directions:
Shell and de-vein shrimp.  Wash shrimp heads well, drain thoroughly.  Heat oil in a saucepan and fry heads and shells of shrimp until they turn pink.  Add hot water, salt, lemon grass, citrus leaves, and whole chilies.  Bring to a boil, cover and simmer for 20 minutes.  Strain stock, return to a boil, add mushrooms and shrimp and simmer for 3-4 minutes or until shrimp are cooked.  Add fish sauce and lemon juice to taste.  This soup should have a pronounced acid flavor, so add sufficient lemon juice to achieve this.  Serve in a large tureen or in soup bowls, sprinkled with sliced chili, cilantro, and spring onions.