“Watch your head,” says chef Alex Stupak half a dozen times as we pick our way among low-hung ducts and overhangs in the extremely unprepossessing basement beneath New York’s Empellón Al Pastor. I am visiting the secret heart of Stupak’s fast-growing group of upscale Mexican restaurants: a small, steamy underground room where, every day, dried corn is made into dough for the exceptionally good fresh corn tortillas that are essential at Empellón.
Upstairs, and in the other Empellón restaurants around the city, where tortillas form the foundation of meals with intense flavors and an avant-garde attention to detail (Stupak spent four years as pastry chef at Wylie Dufresne’s modernist mecca WD-50), most customers likely have no idea that the clever way corn is transformed in the restaurant’s basement room is a technique not significantly changed from Mayan recipes of 1500 BC.
Try shaping ordinary cornmeal and water into a tortilla and you’ll notice a few hurdles right away. First, it doesn’t hold together as a dough no matter how long you soak or cook the grain; it crumbles and slumps into porridge. Unlike wheat, corn contains no gluten, nor any other structural element that would allow it to be shaped into a cohesive mass. Second, it doesn’t smell or taste like tortillas; it has the clean, papery scent of corn, but the familiar tortilla aroma—most familiar to most of us, perhaps, from corn chips—is something entirely different.
The difference is nixtamalization, a process that chemically changes the corn in a variety of interesting ways.
Every night, in the basement of Empellón, the process begins with 100 pounds of dried corn. Less than 5 percent of the world’s corn is the sweet variety meant to be picked and eaten fresh. The rest, used for bourbon, fuel, cereal, masa, and more, is dried in the field before it’s harvested. Empellón buys a flavorful white variety called olotillo blanco that’s grown in Mexico and imported by an heirloom corn wholesaler called Masienda.
The dry corn is brought to a near boil and then left to soak overnight in hot water with an added dose of cal—calcium hydroxide, also known as slaked lime or pickling lime. No relation whatsoever to the green citrus fruit, most slaked lime is produced by heating limestone, which is predominantly calcium carbonate (CaCO3), in an industrial oven, a process called calcination. This breaks the CaCO3 into carbon dioxide and calcium oxide. Adding water to the calcium oxide—“slaking” it—creates calcium hydroxide. Seashells, another source of calcium carbonate, can also be calcinated.
In the morning, the chef drains and rinses the nixtamalized corn (nixtamalized corn is called nixtamal), rubbing off some (but not all) of the loosened outer layer of the kernels.
The wet nixtamal is then milled between a pair of rotating grindstones: corn kernels go in, with a thin stream of water added, depending on the day’s humidity, and a silky, slightly elastic masa dough squiggles out the other end. After a knead to make sure the dough doesn’t have any overly dry or moist patches, it’s fed into a custom-built machine that flattens it into sheets, stamps out circles, feeds them through a series of heated iron conveyor belts, and emits a river of supple, fragrant finished tortillas.