What can I do with the white parts of kale?
Just like the tougher parts of any brassica plant (e.g. broccoli), chop the stems as thinly as required and add to a stir fry dish. they typically take as long as carrots take to "cook" in the wok

Properly grown kale with a decent frost exposure, should have a softer stems with a sweeter and more flavourful taste