This much-loved Chinese soup has a special place in my heart. Purported to have restorative qualities, it’s just what’s needed on a cold winter’s day. Black vinegar delivers a zing of sour and white pepper counters it with subtle heat. The vinegar is imperative, so order the Chinese black variety online if you can’t find it. I’ve kept this meat free, but you can add thin pieces of pork for a more substantial soup.