This is classic pesto, you can adjust ingredients to your liking or play with different herbs and nuts. It is best to use food processor but you might use pestle and mortar.
Blitz the garlic and the basil leaves in the food processor.
Add the pine nuts and the cheese and mix again. slowly pour in the oil while processor is on. The oil should bind the rest of the ingredients but also give it a bit of a runny consistency.
Season with salt and pepper, you might want to add more cheese. Adjust it to your own liking.
Try not to eat the whole batch in one go ;-)
You might add some lemon juice or lemon zest if you want it to be a bit fresher but I tend to stick to basics.