Most Chinese soups are a clear, plain broth, similar to consomme. Hot-and-sour soups are mainly featured in Southeast Asian cuisine, such as Thai and Vietnamese. There is always an exception to the rule, though, and this is a speical one in Chinese cooking. The sour taste comes from rice vinegar and the hot comes from ground white pepper. Chinese white pepper can be surprisingly very hot; too much can be overwhelming and can make a dish inedible.
6 cups vegetable stock
4 to 5 thin slices peeled fresh ginger
1 ⁄ 2 pound firm tofu, well drained and diced
1 ⁄ 2 pound sweet potato, peeled and diced
1 ⁄ 2 pound daikon or jicama, peeled and diced
1 ⁄ 4 pound green beans, cut into 1-inch-long sticks
1 small yellow onion, peeled and cut into 6 to 8 wedges
2 medium tomatoes, cut into 12 wedges
1 bunch watercress or baby spinach, washed and trimmed
1 ⁄ 2 cup tamarind liquid, or more to taste
3 tablespoons light soy sauce
2 red jalape–o or serrano chiles, seeded and chopped
1 tablespoon sugar, or more to taste
1 tablespoon vegetable base (flavor enhancer or bouillon cube)
Salt, to taste
Bring the vegetable stock and ginger to a boil in a large pot over medium heat. Add the tofu, sweet potato, daikon, green beans, and onion. Simmer for 5 to 6 minutes, skimming off any foam or impurities that float to the surface, until the vegetables are almost done.
Add the remaining ingredients, and cook for 2 to 3 minutes longer. Adjust the seasonings to taste.