Inside the Taqueria Bringing Spit-Roasted Tacos to London

The shutters are down when I arrive at recently opened taqueria, El Pastór, in London's Borough Market. But I can hear clattering and the buzz of voices from inside as lunch service in the Mexican restaurant inches closer. Once I'm let in through a small side door, the smell hits me.

More specifically, the smell of slow-cooking, marinated meat engulfs my senses. Its brooding, smoky aroma fills the room, while soft tortillas on a plancha grill provide a corny undertone. I find the source of the meaty smell quickly. In the centre of the open kitchen stands a trompo: the revolving, vertical roasting spit—similar to a shawarma—that mesmerisingly grills dark red pork.

This 24 hour-marinated, spit-roasted pork is the star in El Pastór's signature dish and namesake: taco al pastor.

I've persuaded El Pastór consulting chef Librado Hernandez Alonso to show me what goes into one. As well as pork slices cut straight from the spit and onto a tortilla, the dish comprises grilled pineapple, white onion, coriander, and guacamole.

The taco has another, less tangible ingredient too.

"The first step is to have soul," Alonso says. "Food that is made by happy hands tastes happy. And food that isn't just hasn't got that spark."

The taco al pastor, which roughly translates to "taco in the style of the shepherd," is said to have come about in Central Mexico, thanks to Lebanese migrants who brought with them the technique of spit-roasting shawarma meat.

"The taco al pastor is a deceptively simple-looking creature," explains Crispin Somerville, who opened El Pastór with restaurateur brothers Sam and James Hart at the end of last year. After running a nightclub in Mexico City for ten years in the 90s and early 00s, Somerville and Sam Hart decided it was high time to pay homage to the Mexican capital's food back home in London.

Somerville continues: "But there's so much going on behind it."

Alonso says that getting the marinade right is the next part. He tells me: "The marinade and the quality of meat are important. Especially with the marinade, you're using products that aren't uniform and you have to know the differences in them each morning to create consistency."

I ask what goes into the marinade.

There are rapid exchanges in Spanish, followed by laughter. Somerville explains: "I said, 'We can give her some of the ingredients, right?' and he said, 'What, the wrong ones?'"

Luckily, fellow El Pastór consulting chef Bruno Hernandez Galicia is happier to oblige my question. After some cajoling, he lists some of the marinade elements: "Vinegar, guijillo chili, ancho chili, pasilla chili. There's achiote, which is a red seed and natural food colouring. You can put in some almonds …"

Judging by the colour of the pork, I can 100-percent confirm presence of achiote.

"It's a recipe that's been entrusted to us and of great value in our lives," says Alonso with a smile.

With the meat now sliced onto a tortilla, we move onto toppings. These aren't so secret.

"We add coriander, white onion (a mild Mexican onion so that it's not sulphuric), and a little bit of grilled pineapple," says Galicia. "It's more of a flourish. Because the meat is a deep, dark red, the onions are white, and you've got this shiny piece of yellow on top."

He continues: "And then finally, you add a special kind of guacamole called guacamole taquero, which contains garlic, serrano chili, tomatillo, avocado, and lemon."

Like all great dishes, what binds (literally) the components of a taco al pastor is equally important.

"The tortilla is super important," explains Somerville. "We're having this ongoing discussion with Mexican chef Enrique Olvera about his taco formula: it's 30 percent tortilla, 30 percent salsa, and 30 percent filling. And 10 percent magic!"

The tortillas at El Pastór are all made fresh on site using the nixtamalisation method of soaking and hulling corn in alkaline solution, grinding the kernels, and turning into masa (dough).

Somerville tells me that aside from not using ready-ground corn flour ("Companies add in maize flour and wheat flour, and there was a whole conversation about sometimes fish meal going in"), the restaurant made the decision to use an indigenous corn crop, which has been displaced in many rural areas of Mexico by GM crops.

"GM crops have a higher yield, they're more pest-resistant, and much of Mexican socio-economic structure is based around the price of a kilo of maize from which you make your tortillas," Somerville tells me as Alonso nods in agreement.

Somerville continues: "It's important to keep it at 12 Pesos a kilo. To do a kilo of criollo corn, which is one of the indigenous corns, costs somewhere between 18 and 20. That's why it's no longer a viable crop. But we think it's got a totally different flavour profile and we can afford to produce our tortillas producing criollo corn. And if in some tiny way, we are contributing towards the preservation of an indigenous crop, that's great."

With the first few customers starting to arrive at El Pastór for lunch, it's time for me to leave Alonso and Galicia to their duties—the trompo has been without their careful watch for long enough. Before I leave, I ask why the taco al pastor has such a particular draw for him.

"It's the pressure of getting it right for demanding people," Alonso explains. "On the street side in Mexico, you've got a lot of people demanding their food very quickly. I like that pressure but most of all I like the look of satisfaction that people give when they're discovering a great taco."

Something tells me Alonso won't be short of satisfied faces here.