Step 1

Start the caramelized onions by melting the butter and olive oil together in a large skillet over medium-low heat.

Step 2

Add the sliced onions, salt and pepper to the skillet and toss to coat in the butter and olive oil.

Step 3

Cook, stirring often, for 20-30 minutes until softened and browned.

Step 4

Stir in the marsala wine and cook for 2 minutes more, then remove from the heat.

Step 5

Cook the Texas toast in the oven according to the package directions and let cool.

Step 6

While the Texas toast is in the oven, make the au jus according to the package directions.

Step 7

When you’re ready to make the burgers, take out the hamburger patties and place on your grill. Grill for 2 minutes per side, then top each burger with 2 slices of each different type of cheese to melt.

Step 8

Place a burger on a piece of Texas toast, then top with a large spoonful or the caramelized onions.

Step 9

Repeat with the other two layers, ending with the onions on top and then the top piece of Texas toast.