In a food processor fitted with a metal blade, pulse the herbs, nuts, and garlic until finely chopped.
With the processor running, add the oil in a thin stream.
Season to taste with salt + pepper.
For extra depth of flavor, add 1–2 T rinsed and drained capers, oil-packed sundried tomatoes, pitted olives, or anchovies. You'll need to reduce the amount of sauce you use.
Add 2–4 T Parmesan, Asiago, or other "dry" grating cheese—softer cheeses, such as Cheddar, Swiss, etc., don't work in pesto.
Pesto will last up to a week (or more) in the refrigerator in a tightly-covered glass container. The top layer may turn a bit dark—either scoop it off or simply mix it in.
Pesto can be frozen in tightly-covered containers for up to 3 months. Thaw overnight in the fridge, and give a good stir before using.
Photo by Chuk Nowak, 2016, for Fl!p Your K!tchen® (visit the shop page)