A thick soup with shreds of tofu, wood ear mushroom and often pork, plus ribbons of egg, made sour with vinegar and hot with white pepper rather than chili. Some versions add chili oil.
His hot-and-sour soup has a lot of white pepper in it.
Tips
usage
The 'sour' comes from vinegar (醋), the 'hot' from white pepper (白胡椒) rather than chili - a key difference from mala dishes. Northern and Sichuan versions differ; the Sichuan version 醋椒汤 adds more chili.