5-6 lbs green head cabbage
3T sea salt
Tools and Utensils:
Cutting board and sharp knife
2-3 quart sized Mason jars
Large bowl (do not use aluminum or other reactive metal)
2-3 pint glasses or other clean, heavy weight that will fit inside quart jar
Optional: potato masher or other tool for mashing
Pick out 2 heads of cabbage that weigh about 5-6 lbs. Pull off and save one or two whole leaves, then cut cabbage into quarters removing the core. Finely shred the cabbage into a large bowl. Sprinkle 3 Tbsp salt over cabbage.
Using very clean hands, massage the salt into the cabbage. Use a good amount of pressure, I like to use a motion similar to kneading bread. The goal is to break down the structure of the cabbage and release a lot of the juices. If you have delicate hands, try using a potato masher or other utensil to pack the cabbage down.
When the cabbage is all soft and puddle-y, pack it tight into 2-3 quart sized Mason Jars. Pour any liquid left in the bowl on top of cabbage, equally distributing between jars.
Take the whole cabbage leaves and tear or fold them to fit in the jar on top of the packed cabbage. The goal is to use it as a flap to keep the shreddy bits down.
Now find something to weigh down the cabbage flap. I use a pint glass filled with water. A clean glass juice bottle may also fit. You can also use a zip-top bag filled with brine (1 Tbsp salt to 1 pint of water) and sealed shut. It is important to keep the sauerkraut below the water line. Put your jars on a dish to catch any liquid that may bubble up.
In warm weather (65º-75º F) it may take a week. In cooler weather (55º-65º F) it will take longer. If you start to see a white-ish scum building up, take out your weight and cabbage flap. Skim off any scum you see. Rinse the cabbage flap and weight and replace them. Start tasting your sauerkraut after about a week. When it tastes tangy and delicious, refrigerate to halt the fermentation.
For great info on fermenting read Wild Fermentation by Sandor Ellix Katz.