It’s a Sound. It’s a Sauce. It’s Pil Pil.

Rainbow trout pil pil from Eel Bar. Photo: Hugo Yu

The first time Ryan Bartlow, chef of Ernesto’s on the Lower East Side and the forthcoming Bartolo in the West Village, encountered the Spanish sauce known as pil pil, he was working the mariscos station at Akelarre in San Sebastián. He can recite the recipe, simple as it is, without any trouble (“a shallow rondeau pot with oil, a couple slices of garlic and maybe a dried chile to perfume the oil, toasted gently, without burning …”), but when I ask him about it, he seems more interested in the name of the sauce: pil pil. He says it in a high-pitched voice like the noise a laser gun makes in a cartoon. Pil pil.

The name itself is onomatopoeia, the sound of small elastic bubbles that pop underneath a cod filet slowly cooked in oil. Pil pil is the one of Spain’s most austere mother sauces — garlic-and-chile-infused olive oil mixed with seafood stock and emulsified into what appears to be a loose, pale mayonnaise — and one of those techniques that is a triumph of kitchen resourcefulness, a loose warm cousin of aioli that swaps out egg for seafood protein, which helps the fat of the oil bond with with the flavorful fumet. 

You’re supposed to put your whole self into making the sauce, or as Txikito co-owner Eder Montero says, “You shake your body — it’s a lot of labor, a ritual, a dance.” He and Alex Raij have been serving pil pil in various forms at Txikito since it opened in 2008. The menu usually features no fewer than four pil pil options at any given time, including the classic salt cod, a mild amberjack crudo and a mushroom-based variation for vegetarians. “It took 16 years for people to appreciate, or even accept, this sauce,” jokes Raij.

“Appreciate” could be an understatement. Lately, chefs around the city have become infatuated with the sauce, as interest in casual, seafood-heavy menus rises while the need to find ways to keep costs down is more important than ever. Another upside is that the sauce offers plenty of room for versatility and creative boundary-pushing.

“We’re not traditional, but I definitely want to stay within some rules, boxes, regulations,” says Aaron Crowder, the chef at Basque-inspired Eel Bar and coastal-Portuguese Cervo’s on the Lower East Side. He’s also an avid fisherman, and when he was imagining the menu for Eel Bar, he wanted to include pil pil. But rather than cod, he turned to trout from Pennsylvania for a local twist. He butterflies the fish and places it whole on the plancha. Once it’s nearly cooked through, he lets it sit in lemony, garlic olive oil as it rests.

Crowder’s not the only one applying the pil pil technique to trout. Tomer Blechman is doing the same at Theodora in Fort Greene, first dry-aging the fish for a day or two. While most pil pil is a meditation on subtlety, Blechman brings spice and herbs into the equation: He applies a smoky harissa chile paste to one half of the trout’s flesh and an herbaceous chermoula relish to the other — a red and green flag that spans from Spain to Mexico City while nodding to the latter city’s iconic pescado a la talla at Contramar. It gives color to a dish that can appear deceptively bland in its off-whiteness.

Just off the Lower East Side, chef Fidel Caballero similarly plays with the pan-Latin–ness of the dish at his restaurant Corima. Having spent some time working in Spain, where he first learned how to make pil pil, he puts two riffs on the original template. The first is an infusion of epazote, the oregano-like herb from Mexico, for a tasting-menu hake option. The other is a corn-husk dashi thickened with arrowroot that mimics pil pil’s creamy texture. Fish is then crusted with chives and pipicha, a Oaxacan herb similar to cilantro, and finished with pickled chanterelles and a shimeji vinaigrette.

Will purists sneer? They are, evangelists say, missing the point of pil pil: “San Sebastián became the hub of molecular gastronomy — very modern chefs working there — but you can go to the Basque country and have something very traditional too,” says Ori Kushnir, a co-owner of Foxface Natural in Alphabet City. Along with chef David Santos, they’re testing new concepts in pil pil that are outside of the Basque box with a white-asparagus experiment, a study in squid, and a version made with pig ears. (That last one has been a hit.)

There is no one right way to pil pil, which is what makes it so appealing; it can take any form. “If you go to Asador Etxebarri,” Bartlow says, referencing the Basque destination dedicated to cooking over open flames, “chef Victor Arguinzoniz grills a whole sea bream, opens it up, filets it, debones it, and while it’s still warm, pours olive oil over the flesh side, letting the juices drip onto the sheet pan.”

In the end, success is less about adhering to a formal technique and more about embracing its spirit: “Pil pil is intrinsic to our culture,” says Montero, who is from Bilbao in Spain’s Basque region.  “But pil pil is not even a word — it’s a sound, not something you can write. It’s mythological!”

This post has been updated: Corima’s hake is available on its tasting menu, not à la carte.