Quarter your Napa cabbage lengthwise, then remove the core. Slice each quarter into strips or bite-sized pieces. Place the chopped Napa cabbage leaves into a large bowl.
Sprinkle salt over the chopped cabbage, then massage it until it begins to soften and break down.
Once it softens, add just enough filtered water to cover the cabbage. Use a plate or something similar to weight down the cabbage under the water.Let the Napa cabbage soak in the salt water for about 6 hours, then pour the cabbage into a fine mesh strainer set over a large mixing bowl. Let all of the excess water drain out of the cabbage into the bowl. Reserve the liquid.
In a small bowl, combine ginger, garlic, sugar, fish sauce, ¼ cup of filtered water and Gochugaru pepper. Stir until a chile paste forms. You can leave the garlic a bit chunkier like we like it, or you can make a smooth paste by running it through a food processor.
Transfer the drained cabbage to a large mixing bowl. Add the Daikon radish, green onions and your Kimchi paste.
Wearing food prep gloves to protect your hands from the Korean pepper, massage the Kimchi sauce into the vegetables until everything is evenly coated.
Pack the coated cabbage mixture into mason jars, pressing it down to make sure it’s covered by brine. If there isn’t enough brine in the jar, use the salt water you saved from draining the cabbage to fill it up. Leave about an inch of headspace (it will expand a lot as it starts to ferment) and lightly seal your mason jar with a lid and ring.
Place your jars on top of a towel or in a baking pan (to catch any brine that escapes from the jars) and let them sit for 2-6 days at room temperature out of direct sunlight. Once you start to see bubbling in the mason jar, that means it’s fermenting. Open the jar to release excess pressure and taste your kimchi. If it tastes done, you’ll transfer to the refrigerator. If not, you’ll allow it to ferment for longer. When you close the jar, be sure to press the kimchi back down under the brine.
Once the kimchi tastes done to you, move the jar to the refrigerator for storage. Enjoy your kimchi with your favorite Korean food recipes.