Smash Burgers with Griddled Onions and Spicy Special Sauce
Smash burgers are an iconic staple of American diners, with their toasted buns and that mysteriously delicious special sauce. My version amps up the flavor of the special sauce with pickled jalapenos and adds a slight smoky, sweet flavor from griddled onions. The secret to the perfect smash burger is not overworking the meat so that it's tender and juicy but still gets a browned, salty crust with a hit of pepper and melty cheese draped over the top.
Whisk the mayonnaise, pickled jalapenos, brine, mustard and garlic together in a small bowl. Set aside until ready to serve.
Combine the chuck and brisket in a medium bowl and using 2 forks, "pull" the meat apart, breaking up any clumps and combining the two meats together. This will seem counterintuitive but it will blend the meats together without compacting them. Divide into 4 equal portions and form balls (about the size of tennis balls) being careful not to compact or overwork the meat -- do not form patties.
Heat 2 tablespoons of the oil in a large cast-iron skillet over medium-high heat. Add the onions and season with salt and pepper; cook, tossing occasionally, until golden browned, 6 to 8 minutes. Sprinkle with the sugar and toss until caramelized, about 1 minute. Transfer to a plate.
Increase the heat to high and heat the same skillet until very hot. Add the remaining oil (or 1 tablespoon oil, if working in batches), swirling to coat.
Working in batches if necessary, place balls in the skillet and smash flat with a metal spatula using the handle of a wooden spoon to press down on the spatula to form 4-inch patties (you want to see craggy edges). Season liberally with salt and pepper and cook, undisturbed, until the outer edges are brown, 1 to 2 minutes. Flip the patties, season with salt and pepper and top each patty with a slice of cheese. Cook until the cheese droops and the burgers are medium-rare, about 1 minute.
Serve the patties on the toasted buns with the spicy special sauce, griddled onions, lettuce and tomatoes.