Remove the bottom of the Chinese cabbage and cut the cabbage into 4-centimeter pieces.
Place the chopped cabbage in a large bowl and gently rub the salt all over with your hands. Pour water over it so that everything is submerged and place a plate on top to keep the cabbage down. Wait for 2 hours.
Rinse the cabbage thoroughly in a colander under cold water. Let it drain for 30 minutes.
Mix the ginger, garlic, fish sauce, and sugar into a paste (this can also be done in a blender) and stir in the gochugaru. Let it sit for 15 minutes.
Finely chop the spring onions and half an onion and mix them into the chili paste.
Squeeze out the excess moisture from the cabbage and mix the chili paste around the cabbage well by hand. You may want to use disposable gloves, otherwise it can become painful. (Be careful not to rub your eyes after working with chili paste.)
Press the mixture layer by layer into a large jar. Scrape in any leftover sauce so that the cabbage is well submerged. Seal the jar tightly.
Let the kimchi ferment at room temperature for 2 to 5 days. Since the cabbage may expand during fermentation, it's best to place a small plate under the jar to catch any overflow.
Tips
If it smells strong, it is normal. Then you succeeded! The Kimchi can be kept in the fridge for six months, and very tasty with pancakes or a omelette. Be sure to try it in the cheesy waffles.