In a pestle and mortar, crush the garlic. Add in the pine nuts and crush and stir to create a crumbly paste. Add in most of the parmesan and continue to bash and stir. Start to add the basil, half at a time, crushing it to break the leaves down. Add the remaining leaves and continue to crush and stir.
Slowly add some of the olive oil to begin creating a softer paste. Add more oil, a bit at a time, until a sauce begins to form.
The mixture should be textured and pale green. Add to hot pasta with a little of the pasta water to loosen the pesto. Add the remainder of the parmesan and toss once more.
