Make the kimchi:
Combine salt and water in a large container. Add carrots, beets and cauliflower to the saltwater and soak for 4 hours. Drain, rinse and set aside.
In a food processor, purée garlic, ginger and fish sauce until smooth, like a paste.
In a large bowl, combine the paste with the green onion, radishes and kale.
Add chili flakes and mix well.
Add the saltwater-soaked vegetables to the bowl with the paste and other ingredients. Mix well, making sure that all vegetables have been rubbed well with the paste.
Place in a nonreactive vessel or a ceramic crock. Put a weight on top and place in a dark space for at least 2–4 days. After 2 days, taste the kimchi. When the flavor is right, store covered in the refrigerator.
Steam the fish:
Place each piece of fish in the center of a banana leaf. Sprinkle the fish with a quarter of the garlic, green onion and ginger. Add salt and pepper.
Wrap the fish up like a parcel and place in a bamboo steamer set over a wok or pot filled with boiling water. Steam, covered, for about 10 minutes, until the fish is cooked and its flesh is opaque.
Unwrap the fish. Place a spoonful of kimchi and its juice over the fish and serve immediately. .