Pesto is a typical traditional condiment originating from Liguria. With this name it is included among the traditional Ligurian agri-food products (PAT). Its basic ingredient is basil (Ocimum basilicum), and more specifically Genoese Basil.

Genoese pesto is obtained by crushing (mixing under pressure) the basil with salt, pine nuts and garlic, all seasoned with Parmigiano Reggiano, Fiore Sardo and extra virgin olive oil. It is therefore a raw sauce, i.e. a mixture in which the ingredients are mixed cold, not cooked. Due to this characteristic the ingredients do not lose their original organoleptic characteristics.

The first written recipe can be found in Emanuele Rossi's Vera Cuciniera Genovese (1852), called garlic and basil pesto. Very probably in ancient times, at least in the recipe born in peasant homes, the presence of Parmigiano-Reggiano was not foreseen, as it was a rare cheese on popular Ligurian tables, but only pecorino; not the Sardinian, but the one handcrafted by the shepherds of the Genoese Apennines. On the other hand, the peasant palates of past eras were accustomed to aromas and flavors that were much more intense and, at times, rustic than those of today.

[https://it.wikipedia.org/wiki/Pesto_alla_genovese]