Pesto Genovese

Pesto is not a recipe, it is a technique. The word comes from pestare, to pound, and shares a Latin root with the English word pestle: what the name describes is a sauce made by crushing ingredients in a mortar, which is why Italy has a dozen legitimate pestos. Pesto Genovese is the one from Genoa, and it is built from seven things: Genoese basil, Ligurian extra virgin olive oil, pine nuts, garlic, aged Parmigiano Reggiano, Pecorino Sardo and coarse sea salt.

The protected-designation question is worth getting right, because almost every English-language source gets it wrong. Pesto Genovese itself carries no DOP and no IGP. What the European Union protects, since 2005, is Basilico Genovese DOP, the basil itself. The rules cover where it can be grown (Liguria, below 800 m) and what the leaf must be like, including a clause banning any hint of mint in the aroma.

Sitting on top of that is the Consorzio del Pesto Genovese, a producers' body that owns and polices the phrase Pesto Genovese al Basilico Genovese DOP. That is a collective trademark with its own standard, not a public designation. The practical consequence for a shopper: any jar can legally call itself pesto genovese, and only the Consorzio wording tells you the basil was certified.

Green in the most literal sense: grassy, peppery, with the faint aniseed lift that fresh basil has and none of the dried-herb flavour of jarred sauce. Under it there is garlic warmth, the resinous sweetness of pine nuts, a salty edge from two cheeses pulling in different directions, and the slightly bitter, almost artichoke note of a good Ligurian olive oil.

The texture matters as much as the flavour. Mortar-made pesto is a loose, slightly rough cream, not a purée: you can see leaf fibre and flecks of pine nut, and it coats pasta rather than sitting on it. Blade-made pesto is smoother and duller, because the leaves have been torn and warmed rather than crushed.

The defect to know is mint. Basil that has grown too large or too close to flowering develops a menthol note that the DOP rules explicitly exclude, and once you have tasted it in a bad pesto you cannot unnotice it. If a supermarket jar tastes vaguely of toothpaste, that is why.

The rule that governs everything: pesto is never heated. Not in a pan, not in the oven, not stirred into a simmering sauce. It goes raw into a warm serving bowl, gets loosened with a ladle of the pasta cooking water until it turns into a cream, and only then meets the pasta, off the heat and tossed at the table.

The canonical dish is trofie or trenette with potato and green beans, all cooked in the same pot: diced potato first, beans a few minutes later, pasta last, so everything finishes together. That starchy water is the best thing to loosen the pesto with. Beyond that: mandilli de sæa, the paper-thin pasta squares whose Genoese name means silk handkerchiefs; gnocchi; and lasagne al pesto, layered raw with thin fresh sheets.

The other classic use is minestrone alla genovese, a spoonful stirred in at the end with the heat already off, which turns a vegetable soup into something else entirely.

Quantities run to about 30 g per person, a heaped tablespoon. Some Genoese households soften the sauce for lasagne with a knob of butter or a spoon of prescinseua, the local sour curd. What to avoid: heating it, adding cream, draining the pasta too thoroughly, and buying a food processor's worth at once. Pesto is at its best within minutes of being made.

An unopened shelf stable jar keeps to the date printed on it, a year, in a dark cupboard; a chilled tub carries a much shorter one, two to three weeks. Once any jar is open it goes in the fridge and the working window is short, roughly five to seven days. Level the surface with the back of a spoon and pour a thin film of olive oil over it before closing: the oil seals the basil off from air, and every spoonful needs a fresh film after it.

What air does to basil is visible within hours: the surface oxidises and darkens to brown, and the darkening works downward over days. Chilled olive oil also clouds and solidifies, which is temperature, not the sauce, and it clears at room temperature. Pesto freezes well and this is the standard Genoese solution: freeze it in ice cube trays without the cheese, bag the cubes, and stir the grated cheese in after thawing, since cheese is what suffers most from freezing. Six months in the freezer. Beyond any of this, the date on the pack and the maker are the reference.

Colour is the first read, and it separates two production routes rather than good from bad. Fresh, unpasteurised pesto sold from a chilled cabinet is a bright, slightly greyed grass green and smells of raw basil. Shelf stable jars have been heat treated to survive the shelf, which drives the colour towards khaki or olive and the aroma towards cooked basil. Texture matters too: hand or stone worked pesto stays coarse and slightly grainy, with visible flecks of cheese and nut, while an industrial one is a smooth homogeneous paste.

The label is where most jars abroad give themselves away. The Genoese formula is basil, extra virgin olive oil, Parmigiano Reggiano, pecorino, pine nuts, garlic and salt, and nothing after that. Sunflower or rapeseed oil in place of olive, cashews or sunflower seeds in place of pine nuts, generic hard cheese, potato flakes, added water and preservatives are all common substitutions and all change the sauce. Look for Basilico Genovese DOP named on the front. Price follows honestly: pine nuts are expensive, so a 180 gram jar at $4 has bought something else.

Choose the chilled cabinet over the shelf. Refrigerated pesto with a few weeks of life has usually not been pasteurised, and it is far closer to the real thing than an ambient jar with eighteen months on the date. In the US, Eataly, Italian delis and online specialists carry imported chilled and premium jarred pesto; in the UK, Italian delicatessens and shops such as Sous Chef stock both the sauce and Basilico Genovese DOP-labelled products.

Read the label in this order: the basil percentage (30–40% in serious products), the oil (extra virgin olive oil should come before any sunflower oil, if sunflower appears at all), the nuts (cashews mean no pine nuts), and the additives (potato flakes and lactic acid signal an industrial formula). The phrase Pesto Genovese al Basilico Genovese DOP, the Consorzio's collective mark, is the single most reliable thing printed on a jar.

Prices, roughly: a 6–7 oz jar of imported Italian pesto runs $9–15 in the US and a domestic supermarket brand $4–6, while chilled tubs sit around $7–11. In the UK a 190 g supermarket jar is £2–3.50 and an imported or DOP-basil jar £4.50–8. Making it yourself is cheaper than the premium jar and better than all of them, and the expensive part is the pine nuts, at £50–80 a kilo.

Genoa, and specifically the old town. The trattorie of the caruggi, the narrow lanes behind the port, still serve trofie al pesto made in-house, and the Mercato Orientale is where to see what Genoese cooks actually buy. West of the centre, Prà is the district that gave its name to the best basil in Italy; the surviving greenhouses climb the hillside above the container terminal that took the flat land in the 1990s.

Every two years Palazzo Ducale hosts the Campionato Mondiale di Pesto Genovese al Mortaio, the world mortar-pesto championship: a hundred selected competitors, each with a marble mortar and a wooden pestle, judged on colour, texture and aroma. It has run since 2007 and is open to the public, and worth timing a trip around.

Along the coast, Sori and Recco in the Golfo Paradiso are the places for trofie and for focaccia col formaggio, and Camogli for everything else. Inland at Vessalico, above Imperia, the garlic fair on 2 July is the one day to buy the braided resta. In the Cinque Terre pesto is on every menu and the quality is far more variable than in Genoa.