Prepare the salad: Wash the kale and cabbage leaves well and spin them dry. Remove stems and tough ribs, roll the leaves into a cigar shape and slice them crosswise to make ribbons. Combine them in a large bowl.
Using a julienne slicer (or good knife skills!), julienne the carrot, spring onion, and apple. Add the vegetables and ginger to the cabbage and kale. Sprinkle the salt over top.
Using your hands, rub and squeeze everything together as if you are giving it a massage, until the vegetables begin to break down and release a great deal of their liquid when you squeeze a large handful. If there is not a lot of liquid, keep massaging.
Press the salad: Place a plate directly on top of the massaged vegetables and weigh it down with a heavy object, such as a quart jar filled with water. Let the salad press for about 30 minutes.
When you are ready to eat, drain some of the liquid off the salad, then serve with furikake, a squeeze of lemon and a drizzle of oil if desired. Without oil, this salad keeps very well in the fridge for a few days.