I mentioned kale stem pesto when I wrote about Linda Ly's book. So I recently had collard greens and I decided to see if I could use their woody stems to make pesto. I did whiz the stems first by themselves in the food processor, but then I added walnuts, Parmesan, garlic, salt, a handful of whatever herbs I found in my garden, and olive oil. Delicious! Not woody at all.
November has been very mild, hence the presence of herbs yet in my garden. I'm going to experiment with the pesto again and see if the lack of fresh herbs still makes an agreeable pesto.