Preheat the oven to 220ºC/gas 7.Rinse the kale under cold running water and dry the leaves very well, in a salad spinner if you have one. Cut out the centre stalks, then cut the kale into 5cm slices.Place the kale on a baking tray and drizzle over the sesame and olive oils, scatter over the sesame seeds and season with sea salt and black pepper.Roast in the oven for 20 minutes, turning halfway through cooking, until crisp at the edges.