Cut the cabbage leaves into 1-2 inches pieces. You can tear them by hand or chip with a knife. Remove the core and any very thick pieces. Place the cabbage pieces into a large bowl.
In a large pot or bowl, dissolve the ½ cup of salt into a gallon of water. If it's necessary, you can heat the water to do this, but you must let it cool back down before going on to the next step, otherwise the hot water will kill off the bacteria that’s needed for the kimchi to ferment.
Add your room temperature salted water to the bowl with your kimchi. All of the cabbage should be submerged- add more water if needed. You can use a smaller, clean bowl to weigh down the cabbage if needed. Let the cabbage soak like this for at least two hours.
Drain the cabbage in a colander, and rinse with water to remove the salt.
Place the cabbage into a large, clean mixing bowl. Add the chili powder and mix in any of the additional optional ingredients that you wish to include (see ingredient list above). Mix well. You can add additional water, if needed, to aid in mixing.
Divide the mixture into mason jars, leaving at least one inch of space at the top of each jar. Pack the mixture down gently in each jar. Close the jars, but not too tightly, as the kimchi will release gas it ferments, which needs to escape.
Let the jars site at room temperature for 2-5 days. You should see signs of fermentation after 24 hours. Open the jars at least once a day to let some of the pressure out, and press the mixture back down gently so it stays submerged in liquid.
You can begin taste testing the kimchi on the second day. When you are happy with the amount of sourness, move the jars to the fridge. It can be used right away, but I find the flavor is best after 1-2 weeks in the fridge.
Notes
Note: One medium sized head of Napa cabbage will produce approximately one quart of kimchi. If you are adding several of the optional ingredients, your kimchi batch will be a bit larger. Nutrition information is for the full batch, not including optional ingredients.
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