I'm kicking off the inaugural Chinese Food post with a discussion of hot and sour soup, that workhorse soup at a lot of Chinese joints (second perhaps only to egg drop soup.)
My feeling about hot and sour soup is that—and bear with me here—it should not be hot and it should most definitely not be sour. Most Chinese recipes for the soup concur, though every once in a while I'll duck into a shop in Chinatown serving up a bowl of the soup that lives up to its name. I want to flag down the manager and ask, Didn't you get the memo about hot and sour soup?, but of course I don't.
Hot and sour soup uses ground white peppercorns rather than chili peppers as its "hot" element. Not a particularly fiery spice. For the sour side, it uses just a dash of vinegar made from sweet rice—a type of vinegar that finishes on a sweet, not overtly sour note. (Compare this with tom yum, which uses chili pepper, lemongrass, and lime for a thin broth that is spicy and tangy.)
So if the soup is not hot, and the soup is not sour, then what is it? Hot and sour soup is whatever good stock you have on hand, thickened with cornstarch, containing various bits of meat and vegetables, and finished with vinegar and white pepper. Hot and sour soup is not a thin soup. The liquid is so thick, in fact, that it almost slides across your tongue when you're sipping. That's probably one of my favorite things about the soup, the way the starch slurry adds substance without taste. It's a quality found in a lot of Chinese, particularly Cantonese soups, and it feels very soothing going down the gullet.
What kind of vinegar? Most recipes call for either Chinkiang vinegar, made from glutinous sweet rice, or red vinegar, also made from rice. Chinkiang vinegar is the balsamic of Chinese vinegars. It's sweet with a viscous, inky texture. Red vinegar is more acidic and sharp. I like both and use both depending on my mood.
You can vary what you add to your hot and sour soup. I usually use the dried mushrooms I have on hand: shiitake and wood ears, because I like the contrast between the juiciness of the shiitake and the crunch of wood ear mushrooms. (Wood ear mushrooms are just another kind of fungus; they are shriveled and black when you buy them as dry goods, but they unfurl quite dramatically when reconstituted in water.)
Bamboo and some sort of protein, such as slivers or pork, are common additions to hot and sour soup. Cubes of silken tofu taste good in there, as well as certain squashes, like zucchini. Most things would probably taste good in hot and sour soup. I think of the starchy liquid as a carrier for whatever items may be cut up and lightly simmered.
Most recipes call for both the vinegar and pepper to be added "to taste," presuming, I guess, that some people like their soups more hot and more sour than others. I always start with a judicious two splashes of vinegar and a small spoonful of pepper. Then I sip and adjust. Sip and adjust. How do you now when you've struck the right balance? You'll know. Suddenly the vinegar-y, pepper-y duo becomes one and you'll sip without stopping to think about whether it needs something else. Like love, and happiness, and good fortune, we take the perfect mix of things for granted.