Slice the cabbage head in half. Slice each half again in the middle. Get rid of any tough stalks, but makes sure you still have enough stalk to hold the cabbage leaves together.
Fill a large bowl with cold water. Dunk the sliced cabbage into the cold water, and drain.
Sprinkle a little bit of kosher salt in between each leaf. Place the salted cabbage in a large bowl. Let it rest for 2 to 3 hours flipping it every 30 minutes. This will allow all the leaves to get salted. This process will allow the leaves to stay crunchy after they have been fermented.
Meanwhile, we will prepare the “dressing” that goes on the cabbage. Place the water and sweet white rice flour into a medium pot over medium heat stirring constantly to prevent clumping. Once the rice mixture has reached the boiling point, add in the brown sugar and stir for 2 more minutes. Remove from heat, and let it cool.
In the meantime, while the rice mixture is cooling, and the cabbage is being salted, we can work on our vegetables. If you haven’t sliced your vegetables yet, now is the time to rinse and slice them according to what is stated in the ingredient list.
Place the diced onions, garlic and ginger into a food processor and process until smooth.
Once the rice mixture has completely cooled, add in the processed vegetable mixture, fish sauce (or soy sauce), Korean red pepper flakes, and the diced vegetables. Mix until everything is well combined.
After the cabbage has finished being salted for the required time, fill a large bowl with cold water, and rinse the sliced cabbage several times. Let it drain.
Now for the fun part, you might want to wear some plastic food gloves for this part. I personally don’t, but if you are not used to handling spicy food, you might need to wear those gloves.
Place a little bit of the rice and vegetable mixture between each of the cabbage leaves making sure to entirely cover every cabbage leaf with this delicious mixture.
Place the dressed cabbage into a large glass jar and pack tightly making sure to have the excess liquid rise at the top of the cabbage to prevent spoilage. Place a clean glass weight over the cabbage. Loosely cover the jar with a lid, or if you have a fermentation lid, you can use that too. The objective is to allow the gases being produced during the fermentation process to escape the jar. Place the jar on the counter out of direct sunlight and let it ferment for 3 to 7 days.
Make sure to check on the ferment once a day. Remove the lid, and press the cabbage leaves down to allow more of the ferment liquid to escape to the top, and prevent any air bubbles that might be stuck in between the leaves.
You will know whether your ferment is done or not by the smell and the amount of air bubbles that is being produced at the top. If the ferment smells sour, and you notice a lot of bubbles when you press the cabbage leaves down, then your ferment is ready. At this point, all you need to do is to tightly seal the jar and place it in the fridge. The ferment should be good for several months.