Chef notes
I'm a big fan of truffle, mushrooms and caramelized onions, and they just work so well together on a burger. Add some melted Swiss and a little truffle mayo, and you've got something pretty hard to resist. It's rich, it's savory and exactly the kind of burger I like to eat.
Technique tip: Cook the mushrooms and onions until they are deeply caramelized and most of their moisture has cooked away. For the burger, use a very hot griddle and avoid pressing the patties after the initial smash so they retain their juices while developing a crisp crust.
Swap option: Swiss cheese can be substituted with Gruyère or another mild, nutty melting cheese. Cremini mushrooms can also be swapped for button or wild mushrooms.
Special equipment: Flat-top griddle or cast-iron skillet.
