I wonder if anyone has an idea about this... A couple of weeks ago, I made Cook's Illustrated (the "Soup & Stews" special edition) Caldo Verde recipe, and it worked out great even if I changed it a bit. It used only the leaf part of the kale, and since it was the first time I cooked with the green, I thought it was a shame to spoil all the stems, so I chopped rather finely the stems (maybe 1/4 inch) and put it in the stew at least half an hour before the leaves. I loved it, the stems had the crunchy texture of cooked celery.
I did the recipe again yesterday, but this time I wasn't as lucky. Any idea why? I have noticed that the bunch of kale I used yesterday consisted of branches of leaves attached together rather than separated leaves like the last time. Could that have to do with it?