Toast the pine nuts in a small frying pan for 2-3 minutes, until light golden. Leave to cool.
Tip into a food processor with the basil, crushed garlic and 30ml olive oil. Blitz to a coarse paste. Add the lemon zest and the grated parmesan then blitz again.
Gradually pour in 70ml olive oil, continuing to blitz until combined. Season the pesto and transfer to the fridge until needed.