Sometime in the 1920s, a restaurant opened in El Reno, Oklahoma, called the Hamburger Inn. Its specialty: the onion-fried burger. Not merely a hamburger with fried onions, it is a patty of meat that gets put on the grill with a heap of thinly sliced onions on top. The chef presses down, mashing the onions into the raw meat, and when the burger is flipped, he presses down again. By the time the hamburger is done, the onions and meat have become inseparable—a savory/sweet package with an especially enticing aroma. Dozens of burger restaurants have come and gone in El Reno since then, all opened by cooks who apprenticed at other onion-fried burger joints in town, and today there are four places in the city and a handful in its orbit.
“Onion-fried burger” is not listed on the menu of restaurants that serve it. In El Reno, when you order a hamburger, you will get an onion-fried burger unless you specifically instruct the cook to leave the onions out. All the usual hamburger condiments are available, plus a unique one: El Reno slaw. A pickly-sweet, mustard-colored hash of finely minced cabbage, the slaw is vaguely like relish, and it is more typically used as a topping for the Coney Island hot dogs that also are served at most local burger restaurants.