Pesto been used for all sorts of cold sauces or dips, mostly without any of the original ingredients: arugula (instead of or in addition to basil), black olives, lemon peel, coriander, or mushrooms. In more northern countries, ramson leaves are sometimes used instead of basil. In the 19th century, Genovese immigrants to Argentina brought pesto recipes with them. A Peruvian variety, known as "tallarines verdes" (meaning "green noodles", from Italian "tagliarini"), is slightly creamier, lacks pine nuts (because of their rarity and prohibitive cost in Peru), may use spinach and vegetable oil (in place of olive oil), and is sometimes served
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