Remove the loose outer leaves of the cabbage, then wash.
Quarter each cabbage, and remove the stalk.
Shred the cabbage, I used the 1mm setting on my food processor.
Put the cabbage into large bowls and distribute the salt among them.
Massage the salt into the cabbage. Wait 30 minutes. Massage again. And repeat until a significant pool of salty cabbage juice forms at the bottom of the bowl and the overall volume is half what it was.
Finely chop the ginger and chillis, and mix into the massaged cabbage. Do not massage with bare hands after adding these ingredients.
Sterilise some old jam jars with boiling water. Ensure that the lids are intact and fit well. (It's difficult to judge how many you will need of what size so I prepared a few of various sizes). Allow the jars to cool. Also a jam funnel is very handy for the next stage!
Fill your largest jar, mash down until all the air is removed and brine floats above the cabbage. Repeat until you have a full jar with no air bubbles.
This bit is really important. It is essential that there is no air left in the jar. Put your jar in a bowl and mound up extra cabbage over flowing but within the rim of the jar.
Push down and tighten the lid. If it dribbles purple brine into the bowl then you've removed all the air. Do not reopen. If it didn't dribble then repeat the previous step.
Rinse off your jar and bowl. Place the jar in the bowl. Leave it alone for at least a week. Do not interfere no matter how much the jar cries. It will hiss, bubble and dribble blue and then purple liquid for a few days into the bowl as the brine is replaced by carbon dioxide. Do not open the jar and let oxygen in.
After a week your kimchi is ready. However it will keep for months as long as it is not exposed to air. Once opened keep the jar in the fridge.