I made my first batch of pesto of the season today from the cuttings we took from the basil plants growing on for sale in the greenhouse. When they begin to get tall and lush, we cut them back so they become shorter and more branched and lush. And that means someone (this time me) gets the cuttings to make pesto. Yummy green-ness now resides in my refrigerator and freezer.
I wash the basil leaves in cool water and spin them dry in my salad spinner. Then I put four packed cups of basil, 4 Tbsp of pine nuts, 4 or 5 cloves of garlic, a pinch of salt and 1/2 cup of EVOO (extra virgin olive oil) in my food processor. (You could use a blender, but you'll have to scrape the sides of the blender more often.) I process until it looks pretty well chopped, scraping the sides down as needed. Then I add more EVOO a little at a time until it is a little thinner than I want the final result.
If I'm going to use it right away, I add a cup of freshly-grated parmesan cheese and stir in by hand until blended. If I'm not going to use it right away, I put it into a plastic or glass container and cover it with a thin layer of EVOO to keep the surface from darkening, and store it in the refrigerator or freezer. Then I add the grated cheese right before I'm ready to serve it.