Douzhi (fermented mung bean drink)

Step 1: Rinse 10 ½ oz dried green mung beans and soak in 1 litre of the 4 ¼ cups water in a cool place for 12 hours, until the beans swell and the skins split easily.

Step 2: Drain and blend the beans with 600 ml of the 2 ½ cups water for 2–3 minutes to a fine, foamy batter. Pour through a muslin-lined sieve into a large bowl, squeezing well. Keep the liquid; discard the pulp or use it in pancakes.

Step 3: Stir ½ cup douzhi from a previous batch into the liquid, cover loosely with a clean cloth and leave at 20–77°F for 24–36 hours. The white starch sinks to the bottom, the greyish liquid on top turns cloudy, bubbly and smells pleasantly sour and slightly cheesy.

Step 4: Carefully pour off and discard most of the thin clear liquid from the very top, keeping the soft, sour middle layer and the starch beneath. This thick grey part is raw douzhi. Check it: discard everything if it smells rotten or shows fuzzy or coloured mould.

Step 5: Put 600 ml of the remaining 2 ½ cups water in a pot and bring to the boil over high heat. Stir the raw douzhi well and pour in about 500 ml of it.

Step 6: Lower the heat to medium and stir constantly for 5–8 minutes. As soon as it rises in a froth and turns slightly creamy, take it off the heat; boiling hard makes it split.

Step 7: Meanwhile, shred the 2 ⅞ oz salty pickled mustard root (xiancai) very finely, rinse briefly if very salty, and toss with 2 tsp chilli oil and 1 tsp toasted sesame seeds.

Step 8: Ladle the hot douzhi into bowls and serve straight away with the pickle on the side, sipping between bites. Leftover raw douzhi keeps 2 days in the fridge in a loosely covered container; it grows sourer each day.