Preheat oven to 300F/150C.
Cut away inner ribs from each kale leaf and discard, then tear the kale leaves into same-size pieces. (I made my pieces about the size of a small potato chip.)
Wash torn kale pieces and spin dry in a salad spinner or dry with paper towels until they're very dry. Ensuring they are dry is key for both the flavour and crispiness!
Once completely dry, put kale pieces into a large a bowl. Add 1 T of olive oil, and using your hands distribute the oil evenly on the kale pieces. Add the other tablespoon of oil and continue until all kale pieces are evenly coated with oil and slightly "massaged."
Sprinkle the 2 T sherry vinegar over the kale leaves and spread the vinegar out over all the leaves.
Using two trays, arrange kale leaves in a single layer on a baking sheets lined with parchment paper, then pop the two trays in the oven and roast until they are mostly crisp, about 25 -35 minutes. I checked every 10 minutes or so and turned some pieces over. I also found I didn't mind if there were a few softer parts on some of the kale leaves, I liked the combination of crisp and softer parts.
When chips are done to your liking, sprinkle with a generous amount of sea salt and let them cool.