charles phan's hot and sour shrimp

2 1/2 qt chicken stock
2 oz seedless tamarind pulp
2 whole thai chiles
stemmed and halved lengthwise
6 tbsp avocado oil
2 tbsp garlic
finely chopped
2 tbsp fish sauce
4 tsp freshly squeezed lime juice
1/4 tsp kosher salt
8 oz shrimp
medium, peeled, deveined and cut in half lengthwise
1 half pineapple
medium, peeled, cut lengthwise into 6 pieces, core trimmed away, and cut crosswise into 1/8-inch thick slices, about 1 1/2 cups
3 cups mung bean sprouts
1 1/2 cups bac ha
peeled and cut into 1/8-inch thick rounds, or shredded iceberg lettuce, optional
2 tbsp fresh cilantro
1 tbsp toasted garlic
We make this whenever we can get our hands on bac ha, which is the stem of the taro plant. We usually find it at the Asian market. It kind of looks like styrofoam when sliced, but it has a delicious crunchy texture that holds in the soup. Because the soup base is simmered and strained for the first phase, there's no need to pick out the seeds from the "seedless" tamarind paste. The paste will break up in the hot broth and the seeds will be separated when the soup is strained.
In a large saucepan, combine the stock, tamarind pulp, and chiles and bring to a boil over high heat. Lower heat to a steady simmer for 15 minutes, stirring occasionally with a whisk to break up the tamarind pulp.
While the soup simmers, toast the garlic. Warm the oil in a small saucepan over medium-low heat then add the garlic. Stir and cook for about 5 minutes until the garlic is light golden brown. Watch the garlic carefully to make sure that it doesn't burn.
Place a small fine mesh strainer into a small measuring glass and pour the contents of the pot into it to separate the garlic from the oil. Reserve the oil for rice or salad dressing, see notes.
Once the soup base has finished simmering, remove from the heat. Place a large fine mesh sieve into a large measuring glass (we use a 4 quart one). Strain the soup through the fine-mesh sieve, and discard the solids. Wipe down the pot then pour the liquid back into it.
Stir in the fish sauce, lime juice, and salt and bring to a simmer over medium heat.
Add the shrimp and pineapple and cook for about 30 seconds, until the shrimp just turns pink.
Divide the bean sprouts and bac ha among warmed soup bowls. Ladle the hot soup into the bowls and garnish with the cilantro and toasted garlic, dividing them evenly.
Serve immediately.
source: Charles Phan's Vietnamese Home Cooking
The toasted garlic should be used on the same day it is fried. The garlic oil will keep for about a week in a tightly covered container.