The McDouble is closer to a classic cheeseburger, with two beef patties, a slice of cheese, pickles, diced onions, ketchup, and mustard. The Daily Double, on the other hand, swaps out the classic condiments, pickles, and diced onions for slivered onions, shredded lettuce, tomato slices, and mayonnaise on top of the same double patties and cheese foundation. And the end result is a burger that's more about different textures and a fresher bite than the pure cheesy meatiness of the McDouble.
To properly caramelize an onion, you need to have some patience. We have some tips to avoid common mistakes. Caramelized onions are not often used as a burger topping because they take time to prepare. However, you can speed up the process and have them ready in 20 to 30 minutes instead of as long as an hour. Cook them over low heat with butter and add some brown sugar and soy sauce.