Rinse the cabbage in cool water. Remove the coarse outer leaves and discard. Remove and rinse a few unblemished leaves and set them aside.
Using a large knife, quarter the cabbage and remove the core. Thinly slice the cabbage with a knife or mandoline slicer then transfer cabbage to a large bowl. Make the thin slices as uniform as possible so it will ferment evenly.
Add 1 teaspoon of the salt and, with your hands, massage it into the cabbage. When the cabbage starts to look wet and shiny, taste it. You should be able to taste the salt without it being overwhelming (in other words it should be a little salty but still taste good). Add more salt, a little at a time until this is achieved.
Continue to massage until the cabbage becomes wet and limp and liquid (aka brine) begins to pool in the bottom of the bowl. The brine should run freely when you squeeze a handful of cabbage in your hands.
Transfer the cabbage to a clean 1 quart mason jar (or whatever jar(s) you have on hand) a few handfuls at a time, stopping to press the cabbage into the bottom of the jar using your hand to work out any air pockets before you add more cabbage. Repeat this adding and pressing until all of the cabbage has been packed tightly into the jar. You should have some brine on top of the cabbage once it’s all been pressed into the jar. Leave 2-3 inches of headspace.
Top the packed cabbage with 1 or 2 of the reserved leaves, gently tucking them down along the sides to keep little bits of cabbage under the brine. Pick out any cabbage pieces that are floating at the top of the brine. Exposure to air increases the chances of the kraut developing mold.
Place a zip-top freezer bag into the jar and use your fingers to spread it out so that it covers as much of the cabbage leaf as possible. Fill with cool filtered water and seal while pressing out as much of the air as possible. Tuck the top of the bag into the jar and very loosely screw a lid onto the jar (so that gases created during fermentation can escape) or cover with a clean kitchen towel.
Place vessel on a baking sheet or pan out of direct sunlight and cool (55-75℉) to ferment for 4-14 days. Dark is best but it needs to be somewhere where you won’t forget about it! Check your ferment daily to be sure everything is under the brine.
Taste test your kraut starting at Day 4 by carefully removing the bag with clean hands. Use a plastic or wooden fork to gently push the cabbage leaves aside and remove a small taste. It’s ready when it has a pleasing pickle-y flavor without the strong acidity of vinegar, the cabbage has softened a bit but retains some crunch and the cabbage is more yellow than green and slightly translucent.
If it’s not ready, rinse the bag under running water and carefully place it back in the jar so that all of the cabbage is below the brine. Wait another day or two then taste again to see what you think.
When it’s pleasing to your tastebuds (and/or less than a pH of 4.6 as measured with a pH strip), skim off any scum from the surface and transfer your finished kraut into clean glass jar, tamping it down with your clean hand, a tamper or the handle of a wooden spoon. Pour any leftover brine into the jar. Tighten the lid then refrigerate for up to 6 months to 1 year.