Contents
Pesto means "pounded" — the name is the method, not the ingredients. The Genoese original, pesto alla genovese, is basil, pine nuts, garlic, Parmesan, Pecorino Sardo, salt and Ligurian olive oil, worked in a marble mortar.
In cold food it does two jobs at once: it is a flavour and it is the fat barrier that keeps a sandwich dry — see caprese sandwich.
Why the mortar matters
A food processor's blades cut and heat the basil, bruising the cut edges and oxidising them; the pesto goes dark khaki within the hour. A mortar crushes and tears, releasing oils without the same bruising, and the colour and flavour both hold longer. If you use a processor: chill the bowl, pulse rather than run it, and add the oil by hand at the end.
Blanching the basil for five seconds and shocking it in ice water keeps it bright green for days. Purists object; it works.
Buying
Jarred pesto is usually made with sunflower oil and cashews rather than olive oil and pine nuts, and often with far more cheese and acid than the original. It is a reasonable ingredient on its own terms — just not the same thing. Refrigerated fresh pesto beats the ambient jar.
Variations worth knowing
- Pesto rosso — sun-dried tomato, almonds. Sicilian, and better in a cold pasta salad than the green one.
- Pistachio pesto — Sicilian, richer, excellent on bread.
- Any soft herb and any nut works on the same formula: herb, nut, hard cheese, garlic, oil, salt. Parsley and walnuts is the cheapest good version.
Keeping
Homemade, a week refrigerated under a film of oil — exposed surface goes black. Freezes very well in an ice-cube tray; leave the cheese out and add it on thawing.
Elsewhere on the site
Used in: caprese sandwich · cold pasta salad · italian sub
Related: basil · olive oil · walnuts · fresh mozzarella · sauces