START TO FINISH: 35 minutes
SERVINGS: 4
The chivito is the national sandwich of Uruguay, and it served as our inspiration for this recipe. Ours is a pared-down version of the classic, which typically includes mayonnaise, lettuce, tomato, sliced hard-cooked eggs, ham and/or bacon. Olives are another common filling, but we opted instead to make an onion-olive-cilantro relish that keeps the flavors fresh and bright. We liked the buttery tenderness of beef tenderloin, but pork tenderloin is a less pricey alternative. If using pork tenderloin, trim off the silver skin, cut the tenderloin crosswise into ½-inch-thick slices and cook similar to the beef tenderloin, but increase timing to about 2 minutes per side.
Don’t use preshredded mozzarella, as it’s usually coated with anti-caking agents. Purchase a chunk and shred your own. Also, don’t use the variety packed in water, as it has a high moisture content and is not a good melting cheese.
Four 6- to 8-inch hoagie or sub rolls, halved lengthwise
5 tablespoons grapeseed or other neutral oil, divided
10 ounces shredded mozzarella cheese (3½ cups)
½ large red onion, minced
4 large pimento-stuffed green olives, minced
1 jalapeño chili, stemmed and minced
½ cup lightly packed fresh cilantro, finely chopped
4 teaspoons red wine vinegar, divided, plus more if needed
Kosher salt and ground black pepper
2 tablespoons soy sauce
1 pound beef tenderloin, trimmed of silver skin and cut crosswise into 8 medallions (each about ½ inch thick)
Heat the oven to 450°F with the rack in the middle position. Line a rimmed baking sheet with foil. Brush the outsides of the rolls with 1 tablespoon of the oil, then arrange the halves cut side up on the prepared baking sheet. Divide the cheese evenly among the 4 top halves.
In a heavy-bottomed 12-inch skillet over medium, heat 2 tablespoons of the remaining oil until shimmering. Add the onion and cook, stirring, until softened, 2 to 3 minutes. Transfer to a small bowl and let cool slightly; set the skillet aside. Stir in the olives, jalapeño, cilantro, 2 teaspoons of the vinegar and 1 teaspoon salt. Taste and season with salt and additional vinegar if needed, then set aside.
In a medium bowl, combine the remaining 2 teaspoons vinegar, the soy sauce and ½ teaspoon pepper. Add the steak and turn to coat. Let stand at room temperature for 5 minutes, then remove the pieces and pat dry with paper towels.
Transfer the rolls to the oven and bake until the cheese has melted, about 5 minutes. Meanwhile, in the same 12-inch skillet, heat 1 tablespoon of the oil over high until barely smoking. Add half the beef in an even layer and cook undisturbed until well browned and the meat releases easily from the pan, 1 to 3 minutes. Using tongs, flip the meat and cook just until the second side is no longer pink, about 1 minute. Transfer to a plate and repeat with the remaining 1 tablespoon oil and the remaining beef.
Evenly distribute the onion mixture among the bottom halves of the rolls, then layer 2 pieces of beef on each. Cover with the tops of the rolls.