In 1944 the New York Times mentioned an imported canned pesto paste. In 1946 Sunset Magazine carried its first pesto recipe, perhaps the first published by a major publication in the United States. This recipe was from Angelo Pellegrini, an English professor and author of The Unprejudiced Palate. However, pesto sauce did not become popular in North America until the 1980s and 1990s.
Historically, pesto was (and is sometimes still) prepared in a marble mortar with wooden pestle. First the basil leaves are washed and dried and then put in the mortar together with garlic and some coarse crystals of sea salt, crushed to a creamy consistency. Then the pine nuts are added and crushed together. When the pine nuts are well incorporated in the "cream", the two grated cheeses (Parmigiano e Pecorino) plus olive oil can be added and stirred together with a wooden spoon. The sauce is now ready. In a tight jar, or simply in an air-tight plastic container, pesto can last in the refrigerator up to a week. Pesto can also be frozen, if needed.
Commercial, lower-quality pesto, usually sold in small jars, is commonly available in stores in green (original) or red (with sun-dried tomatoes or red bell peppers) varieties, produced by major manufacturers or under a 'generic' or 'cheaper' brand. In this quality pesto, cashew nuts or walnuts are often used instead of pine nuts, because they are less expensive and have a similar texture. Cheaper oils may also be used.
Pesto is commonly used on pasta, traditionally with Mandilli de Sea (Genovese dialect - literally "silk handkerchieves" - for lasagna), strozzapreti or trenette. It is sometime used in minestrone as well. It is very important never to cook pesto because basil when heated gets bitter. Pesto is also often served on sliced beef, tomatoes and sliced boiled potatoes.
Sometimes almonds are used instead of pine nuts, and sometimes mint leaves are mixed in with the basil leaves.
Other existing ingredient variations include: arugula (instead of or in addition to basil), black olives, lemon rind, coriander or mushrooms. A German variety uses ramsons leaves instead of basil. In the 19th century, Genovese immigrants to Argentina brought pesto recipes with them. A Peruvian variety, known as "Tallarin Verde" (literally "Green Noodles", from Italian tagliarini) is slightly creamier, uses spinach leaves and is served with potatoes and sirloin steak.
Vegan variations of pesto can include mixes of fresh basil, walnut, olive oil and miso paste.