Add the basil leaves, pine nuts, garlic, salt, and pepper to the food processor and chop/puree/blend for about 20 seconds. I like to add the garlic already minced just so that it's finer in the mixture and it incorporates easier, but you can also add it whole.
Add the grated parmesan and process it/blend it until it’s all very finely chopped (it should take less than a minute).
After everything has been finely chopped in the processor, while processing/blending, slowly add the olive oil. Adding it slowly while blending/processing helps emulsify the pesto.
Taste the pesto and adjust it to your preference, adding more parmesan, salt, garlic, or olive oil to taste.