In food processor bowl combine basil, spinach, Parmesan cheese, pine nuts or almonds, garlic, and, if desired, salt. Cover and process with several on-off turns until a paste forms, stopping to scrape down side as necessary. With machine running, gradually add oil and water. Process to the consistency of soft butter. Store in refrigerator up to 2 days or in freezer up to 1 month. Makes 1/2 cup pesto.