Wash the cabbage and peel off a couple outer leaves of the cabbage to reserve for later. Cut the cabbage into quarters, slice out the core, and slice it as thin as possible. I use the slicing blade on my food processor on one of the thinner settings (but not the absolute thinnest).*
Get a really big bowl for the cabbage and toss it with the salt. You may need to add in some of the cabbage and salt halfway through, once it shrinks down, unless you have the biggest bowl ever.
Let it sit for 10 minutes.
Use your hands to massage the cabbage and salt together really well. Squeeze it a lot. It will take several minutes. Do it until the cabbage is fairly limp and you’ve released a lot of liquid.
Mix in the caraway seeds.
Pack it in to a jar or two; you’ll need about 2 litres’ worth of space. Really pack it in. There should be liquid covering the cabbage, too.
Take one of the reserved leaves and cover the cabbage with it. This will prevent the shreds from floating to the surface and getting moldy; if they aren’t submerged, they won’t stay preserved. If it seems necessary (depending on how tightly everything is packed), you can put a small jar or a stone on top of the leaf to keep it in place.
Cover the jar and let it sit on the counter for 4 to 6 weeks. If you have a warmer home, it will ferment closer to the 4 week mark. Less than that, and it may not develop all the different types of healthy bacteria, because different strains develop at different points in the fermentation process. You can open it to smell or taste as often as you like and decide when it’s reached the level of sourness you want.
IMPORTANT: You will need to “burp” the jar each day for the first week or so, meaning opening the lid to release the bubbles. There is a lot of gas buildup when the fermenting process starts, and the jar could explode otherwise. You will see it bubble each time you open it. Once it stops doing this every day, you can stop burping it.
*Sometimes, I leave a little cabbage fresh and make it into a slaw, because I find I can’t always fit the whole cabbage in my jars (although I recently found an extra-big jar; see the top photo in this post).