Pesto became a staple in the Ligurian culinary tradition, with each family often featuring its own pesto recipe (with slight differences to the traditional ingredients). This is the main reason why pesto recipes often differ from each other. In 1944, "The New York Times" mentioned an imported canned pesto paste. In 1946, "Sunset" magazine published a pesto recipe by Angelo Pellegrini. Pesto did not become popular in North America until the 1980s and 1990s. Pesto is traditionally prepared in a marble mortar with a wooden pestle. First, garlic and pine nuts are placed in the mortar and reduced to a cream,
Pesto then the washed and dried basil leaves are added with coarse salt and ground to a creamy consistency. Only then is a mix of Parmigiano-Reggiano and Pecorino added. To help incorporate the cheese a little extra-virgin olive oil is added. In a tight jar (or simply in an air-tight plastic container), covered by a layer of extra-virgin olive oil, pesto can last in the refrigerator up to a week, and can be frozen for later use. Pesto is commonly used on pasta, traditionally with "mandilli de sæa" ("silk handkerchiefs" in the Genoese dialect), trofie or trenette. Potatoes and string beans