Hong suan tangFermented tomato sour soup base
In the Miao and Dong villages of Qiandongnan, south-east Guizhou, small wild 'hairy' tomatoes and red chillies ripen together in late summer, and every household fills tall jars with them to ferment into hong suan tang, the red sour base of the region's famous sour-soup fish and sour-soup beef hot pots. The fermented paste is bright scarlet, sharply sour, fruity and fiery, with a funk from the ferment that ordinary tomato never has. People say three days without sour and you walk unsteadily, and it goes into soups year round. Outside Guizhou, use cherry tomatoes, which have a similar high acidity. Common mistake: fermenting with too little salt or with wet produce, which goes mushy and off; dry everything first and weigh the salt. Normal signs: bubbles, a sour, wine-like fruity smell and liquid rising. Bad signs: fuzzy coloured mould, pink or black patches, or a rotten smell; discard. It is ready after 2–3 weeks, when it tastes clearly sour and the raw tomato taste has gone. Then keep it in the fridge for 3 months or freeze it. Chef's tip: fry a few spoonfuls in oil with ginger before adding stock; it turns a deeper red and smells richer.

































































































