Soak the lump tamarind in the boiling water for 15 minutes, or until the
tamarind is soft. (Place the whole lump of tamarind and seed in the water and let soak till cool enough to handle. Work the pulp with your fingers to get it to dissolve into the water).

Assemble your ingredients.

Cut each shrimp lengthwise in half. In a bowl, combine the shrimp, garlic,
1 teaspoon of the fish sauce and pepper to taste. Let stand for 30 minutes.

Heat the oil in a 3-quart saucepan. Add the shallots and lemon grass and
saute briefly, without browning.

Add the tomato and sugar and cook over moderate heat ...

until slightly soft.

Add the pineapple and bamboo shoots and cook, stirring, for about 2
minutes.

Add 5 cups of water and bring to a boil over high heat. (I boiled the shrimp shells in about 6 cups of water and used that broth).

Stir in the tamarind liquid, salt and the remaining 1/4 cup fish sauce.
Reduce the heat to moderate and simmer the broth for 5 minutes.

Stir in the shrimp, chiles and bean sprouts and cook for 30 seconds more.

Add the scallion and mint. Remove from the heat. Remove and discard the
lemon grass.

Ladle the soup into a heated tureen and serve at once.
Note: Do not overcook the shrimp or they will toughen. Catfish, red
snapper or any other firm white-fleshed fish can replace the shrimp.

Tamarind is made from the interior pulp of a tree seed pod and is
quite sour. It has a subtly sweet taste too. I've never done it,
but I imagine that you could substitute lemon juice for the tamarind
and still retain the essential character of the soup.

Lemon grass can be replaced by grated lemon zest with a bit of
juice--it's the lemon taste rather than the sourness that's wanted
here. Dried lemon grass is available and is virtually as good as the
fresh stuff. It's inexpensive and keeps well on the shelf. (I grow
my own lemon grass--it's a really easy and pest free plant to grow.
If you manage to find some fresh lemon grass, whack off the bottom
couple of inches and stick it in a flower pot full of good potting
soil. Don't water the cutting too heavily until it starts to grow.
Chances are that it will take off and then you can transplant it into
the ground--it likes rich, well drained soil and full sun.)

There's NO substitute for fish sauce. The soup would probably be good
without it, but it wouldn't be the same.

Since there's not that much difference between canned and fresh
pineapple (at least here on the mainland) I use canned stuff, drained
and chopped. If you're ever in a market and see fresh Thai pineapple,
grab some. The stuff I had in Thailand made our Hawaiian pineapples
pale in comparison.