A classic traditional Italian recipe for pasta sauce originating in Genoa in the Liguria region of northern Italy (pesto alla genovese), and traditionally consists of crushed garlic, basil and nuts  blended with olive oil and cheese.  Italians prefer Ligurian basil, because of its discreet flavor and the  absence of a minty taste.  For best results, prepare all the ingredients in advance and keep in room temperature. It would be best if you enjoyed your pesto right away.  However, you can put pesto in glass jars in the refridgerator, pouring extra olive oil on top for preservation.