An uncooked sauce made with fresh basil, garlic, pine nuts, parmesan or pecorino cheese and olive oil. The ingredients can either be crushed with mortar and pestle or finely chopped with a food processor. This classic, fresh-tasting sauce originated in Genoa, Italy, and although used on a variety of dishes, it is a favorite with pasta. Now there are "pestos" made from myriad other ingredients from cilantro to mint.