Toast the pine nuts in a dry skillet on medium heat until golden brown, about 5 minutes.
Place the lemon juice and garlic in the bowl of a food processor and blend.
Add the basil leaves in 2 - 3 lots, blending in between until finely chopped.
Add the pine nuts and cheese (if using) and process until well blended.
With the machine running, drizzle in the olive oil and process until smooth.
Add more olive oil to get your desired consistency. I find ¼ cup is never enough. I like it to be a thicker paste so I can thin it down with some pasta cooking water.
Taste for seasoning and add more salt if needed.
Mix through your cooked pasta with a splash of pasta cooking water.
Add some extra fresh basil, a squeeze of fresh lemon juice and some toasted pine nuts to serve.