2 pounds fresh mushrooms (or other ingredient) cut into convenient
 spoonable size pieces...
 
 2 stalks of lemon grass, bruised (this isn't eaten, but is an essential
 flavorant)
 
 2 “kaffir” lime leaves (use lime zest if you can't get it)
 2 coriander [cilantro] plants, chopped.
 10-15 prik ki nu (birdseye chilis) thinly sliced.
 2-5 dried red chilis.
 the juice of 3 or 4 limes
 2 or 3 tablespoons of sliced bamboo shoots or coconut shoots
 2-3 tablespoons of fish sauce.
 1-2 tablespoons “chilis in oil”
 The fresh chiles should be bruised in a mortar and pestle. The dried
 chilies should be heated first, then crumbled into the fresh chilies.
 Beat the lemon grass with the grinder of the mortar and pestle (it’s
 called a 'sa' in Thai, I'm never sure whether it is the mortar or the
 pestle in English...) or the back of a cleaver.
 
 Heat about 3 cups of water to boiling point, add all the ingredients,
 and stir constantly until cooked (it doesn't take long for mushrooms,
 longer for chicken or shrimp, and longest for beef).
 
 variation : use three cups of thin coconut milk instead of water, the
 result is tom kha, rather than tom yum...