Bring a large pot of water to the boil with the salt. Boil the pasta according to pack instructions. Scoop out 300 ml water and set aside. Drain pasta in a colander.
Combine the ingredietns for the Pesto in a blender and blend till combined. Add 75 ml water and blend again.
Add the pesto to the pasta in a large bowl and combine, adding more water if required to make the sauce silky.
Taste the salt and add more if needed. Divide between bowls and add additional parmesan, spinach and pine nuts.
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