"Very tasty, quick, and easy pesto. We use it on soups and sandwiches. It's ready to use right away but I like to make it a day or two before I need it so the flavor can develop. I usually use my Ninja® since its easier to clean than the food processor."
Process walnuts, parsley, sage, and garlic together in a food processor until coarsely ground. With the food processor still running, slowly stream olive oil into the mixture until completely integrated into a smooth mixture. Add Pecorino Romano cheese, salt, and pepper; continue to process until the mixture has the consistency of a loose paste.