Step 1

Preheat a griddle or large skillet over medium-high heat.

Step 2

Place the cheese sauce in a pan over low heat to warm gradually.

Step 3

Melt the butter on one half of the griddle. Add the onion, peppers and mushrooms to the buttered side of the griddle and toss. Season with 1 teaspoon of the steak seasoning, then let cook until they begin to caramelize and darken, 8 to 10 minutes.

Step 4

Meanwhile, divide the beef in half and roll each half into a ball. Sprinkle the beef with the remaining teaspoon steak seasoning, along with some salt and pepper. Add the beef to the griddle and, using the back of a spatula, smash the beef into two thin patties. Cook for 2 to 3 minutes per side. When the patties are cooked through, place a slice of provolone on each patty and allow to melt slightly. Place one patty on top of the other and remove to a plate. Remove the vegetables to a plate also.

Step 5

Add the mustard to the bottom half of the roll. Add the patties and top with the vegetables. Cover the vegetables with the cheese sauce and add the top half of the roll. Serve immediately.