Today we're making the best smashburger recipe ever! My double patty smashburgers are seared in bacon grease and mustard, then topped with melted American cheese, caramelized grilled onions, and served on a toasted buttery brioche bun!
On your flat top grill, caramelize the onions in about 1 tablespoon of bacon grease or oil. It’s going to take a good 20-30 minutes until the onions are charred and caramelized.
Remove the onions to a bowl, and add your burgers to the grill. Sear the balls on both sides, then after a few minutes, give them a good smash with a large grilling spatula.
Season the burgers with a little salt and pepper on both sides.
Next add your desired amount of mustard to both sides of the patties and flip to seal in the flavor.
Finally, add two slices of American cheese to each patty and close the grill to allow the cheese to melt.
Toast your brioche bun on the griddle.
When the smash burgers are at your desired doneness, remove them to a serving plate.
Build your smash burger. First, add one patty to the toasted bun. Add a little bit of the mustard drippings from the pan, add some grilled onions, top with the second burger, more onions, and then the brioche on top.