Pesto means Italian sauce. Originated in Italy, in the Liguria region in Genoa (pesto alla Genovese). In the Roman times it is believed that it was imported from Africa. Made from the basil leaf. Traditional ingredients in pesto are usually; basil, garlic, salt, pine nuts, extra virgin olive oil, parmigiano reggiano, cow cheese and sheep cheese. Commercial pesto contains walnuts or cashews because they are cheaper. Somewhat cheaper cheeses may be replaced in commercial pesto as well. Pesto can be used for a sauce for meat or pasta, or on toasted bread.
Pistou sauce is the French version of Italy's pesto.
Commercial pesto is sold in grocery stores year round.
Once pesto is made at home from scratch it can be kept in the fridge for up to 4 weeks in a covered container. Pour a thin film of olive oil on top of the pesto to prevent discoloration. If you intend on storing it longer, do not add the parmesan cheese if using, add that when you serve it.