To make the kale pesto, put the kale in a food processor with the olive oil, zest and juice of the lemon, garlic and parmesan, then whizz to a fine paste. Season with salt and pepper, taste and adjust the flavour with a little more lemon juice or olive oil if needed.
To make the pangrattato topping, put a splash of olive oil in a large frying pan over a medium heat and toast the fresh breadcrumbs with a pinch of salt until golden, then stir in half the kale pesto, the toasted pine nuts and chilli flakes. Turn off the heat.
Cook the spaghetti according to the pack instructions and drain, reserving a cupful of cooking water. Toss the remaining pesto with the pasta and a splash of reserved cooking water, then toss with the kale pangrattato. Sprinkle with extra lemon zest, grated parmesan (or vegetarian alternative) and chilli flakes, then serve with lemon wedges for squeezing.