Put the ingredients in a pot and just simmer for 15 minutes - it's an easy recipe. You can do that because you're using winter cabbage.
I was wondering about the difference between spring and winter cabbage, and made this dish. Winter cabbage has a stronger flavor, and it still has a nice texture after simmering!
Season with salt and pepper to taste. The soup is delicious too, so please have that as well.
Enjoy Japanese food around the world.