Hot and Sour Soup (Suan La Tang)

This soup doesn't look like much - in fact, it kind of looks like gruel (or something equally gross).  But it was actually one of my favorite soups we have made all year.  It had a ton of flavor and a wonderful rich texture.  I'm not really sure how to describe the texture, except to describe it as slightly unctuous.  I know that unctuous can be an unappealing adjective to describe food, but I can't think of a better way to describe the soup.  And hot and sour soup is supposed to be a little unctuous.  The cornstarch slurry did its job in thickening the soup a little, but I think a lot of the texture also had to do with the richness of the homemade broth we used from our Chicken Pho (Pho Ga).  When we took the broth out of the fridge to use it, it already had some body to it.  Actually, it almost appeared to be verging on gelatinous in its chilled form.  It actually jiggled.  And even once we heated the broth up, it retained a lot of that richness, as well as the complexity of flavor that I babbled on about in my post about the pho.  And after we added in all of the additional ingredients, the soup was beautifully complex, yet balanced.  The dried mushrooms added a touch of earthiness and umami, the vinegar added the sourness and bite that you want in a hot and sour soup, the white pepper added a hint of heat, the eggs added creamyness to the already rich broth and the scallions/cilantro on top added a little brightness.  It was awesome.  I heart this soup. 

Recipe after the jump!

 
Hot and Sour Soup (Suan La Tang)
Adapted from The Asian Grandmothers Cookbook: Home Cooking from Asian American Kichens
By Patricia Tanumihardja

INGREDIENTS:
4 cups chicken stock (or vegetable stock if you want this to be vegetarian)
light soy sauce
3 tbsp white vinegar
1 tsp ground white pepper
3 oz firm tofu, cut into 2- by 1/4- by 1/4-inch strips
1/2 oz dried wood ear mushrooms, soaked in hot water to rehydrate, and sliced into 1/4-inch ribbons
4 small dried shiitake mushrooms, soaked in hot water to rehydrate, and sliced into 1/4-inch ribbons
2 tbsp cornstarch, dissolved in 2 tbsp cool water
2 large eggs, lightly beaten
sesame oil
1 scallion, white and green parts, thinly sliced on the bias, for garnish
2 tbsp cilantro, finely chopped, for garnish

Combine stock, 3 tbsp light soy sauce (or to taste), vinegar and white pepper in a large pot (we used our Le Creuset like we always do).  Add tofu and mushrooms.  Bring to a boil over high heat.  Reduce the heat to medium.  Add the cornstarch slurry slowly into the soup, stirring constantly until the soup has thickened and returned to a boil, about 2 minutes. 

Moving in a circular motion around the pot, pour the beaten egg into the soup through the tines of a fork (or a pair of chopsticks) to help it flow in a slow steady stream.  You want the egg to form wispy strands, not a large lumpy mass.  Gently stir in one direction to integrate the egg into the soup.

Remove from heat.  Taste and adjust seasonings as necessary.  Ladle soup into individual bowls, drizzle with sesame oil and garnish with scallions and cilantro.