Remove the outer leaves of the Napa cabbane. Cut of the edges. Seperate the leaves. Keep aside 3-4 leaves and then chop the rest into quarters.
In a large skillet, add the 10 cups of water along with salt. Give it a swirl and then soak the cabbage leaves for 6-8 hours.
After soaking, remove the leaves, wash/rinse in cold water and squeeze out any excess water. Set the salted water aside. Dont throw it away. Slice the daikons into matchsticks. Chop the mustard greens if using. In a bowl, add the ginger garlic paste and the chilli powder -
make it into a paste by adding about 1/2 cup of water.
To this paste, add the daikon,scallions,mustard greens and mix until blended. Gloved hands are your best bet.
now add the squeezed out cabbage and blend it along with the rest of the chilli mixture.
Take one of the leaves ( which has not been chopped), set it on the board. Put few spoonfuls of this spiced mixture on it.
Now place another cabbage leave as a layer above it and then repeat the process until all the leaves have been used.
Take a Jar and lift this napa-spice layers and push it down the jar. Pack it tightly.
Add any additional mixture to the jar on top.
Use the salt water (used for soaking the cabbage) and pour it down the jar to the brim.
Set aside this jar for 2-3 days ( for the process of fermentation) and then enjoy it with rice or any other korean main dish. There you just made yourself an authentic spicy korean vegetable preserve.