You’ll need a 1.5 litre preserving jar with an airlock lid for this recipe. Wash the jar and all utensils in very hot water or run them through a hot rinse cycle in the dishwasher.
Remove the outer leaves of the cabbage. Choose one, wash it well and set aside. Cut the cabbage in half lengthways, then cut crossways into 5 cm pieces, discarding the root end.
Combine the cabbage, choy sum, spring onion, coriander and chopped and halved chillies in a large glass or stainless steel bowl, sprinkle on the salt and mix well.
Add the garlic, ginger, chilli powder and fish sauce. Mix well, cover and set aside.
Dissolve the starter culture in fi ltered water according to the packet instructions (the amount of water will depend on the brand). Add to the vegetables and mix well. Fill the prepared jar with the vegetable mixture, pressing down well with a large spoon or potato masher to remove any air pockets. Leave 2 cm of room free at the top. The vegetables should be completely submerged in the liquid; add more filtered water if necessary.
Fold the clean cabbage leaf, place it on top of the cabbage mixture and add a small glass weight (a shot glass is ideal) to keep everything submerged. Close the lid, then wrap a tea towel around the side of the jar to block out the light.
Store in a dark place (e.g. an esky) at 16–23°C for 8–15 days (add another 5 days if not using the starter culture). See Notes on page 96 for more information about vegetable culturing times. Chill before eating. Once opened, the kimchi will last for up to 2 months in the fridge when kept submerged in the liquid. Unopened, it will keep for up to 9 months in the fridge.