Preheat the oven to 200ºC/gas 6.
Rinse and dry the kale leaves before removing most of the centre stalk, leaving long, thin pieces of kale.
Toss the kale in the oil, then sprinkle with the sugar, cinnamon and ½ tablespoon of sea salt.
Arrange the leaves in a single layer on a couple of baking trays and bake for 5 minutes, until crisp.
Transfer the kale to a rack to cool, then serve.