Dry-fry the pine nuts until golden. Set aside.
In a deep saucepan bring some water to the boil. Add the spaghetti and cook it until al dente (normally about 10 minutes but check the instructions on the packaging).
In the meantime, remove the hard stalks of the kale, then roughly chop. Put half of the kale in a small food processer. Add the basil, pine nuts, cheese, lemon zest & juice and garlic, then blend until you get a rough paste. Then turn down the heat and add the olive oil slowly until you get a more creamy constancy (but it should remain textured).
For the last minute of the cooking time add the remaning kale. Drain the pasta and kale, return to the pan and mix with the pesto.
Serve with extra grated Parmesan and plenty of freshly ground peppercorn.