Oklahoma’s famous onion burger is made by smashing caramelised onions into one side of a beef patty as it cooks, topping the patty with cheese, then slotting the whole lot into a bun. It was naturally born during the Great Depression, as cooks everywhere bulked out burger patties with cheaper extenders. Ross Davis of the Hamburger Inn in El Reno is credited with creating the dish, which is perhaps more popular today than ever.

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Last updated by Jessica Morris.

Fabulous foods born from hardship that became firm favourites