Smashburger Truffle Mushroom Swiss

Burger Seasoning
2 teaspoons kosher salt
2 teaspoons ground black pepper
2 teaspoons seasoned salt
Truffle Mayonnaise
1/2 teaspoon truffle oil
1 cup of mayonnaise
Mushrooms and Grilled Onions
1 cup sliced white onions
2 cups sliced Cremini mushrooms
1 1/2 tablespoons butter
2 1/2 pounds of ground chuck
8 slices of swiss cheese
4 hamburger buns (use egg buns if available)

Prepare the burger seasoning by combining the kosher salt, black pepper, and the seasoned salt in a small container. You will use the burger seasoning for both the burgers and the mushrooms and onions.

Prepare the truffle mayonnaise by combining the truffle oil and mayonnaise in a small container and set aside. You will have some left over. You may want to dip your fries in the extra mayonnaise.

Divide the ground meat into 8 equal portions of beef. Press the beef into round balls.

Prepare the mushrooms and onions by heating up the skillet to medium-high. Add butter, when the butter has melted sear the mushrooms and onions. Season the mushrooms and onions with a pinch or two of the burger seasoning. Cook the mushrooms and onions by flipping occasionally and when they have begun to brown remove from the pan and set aside.

Do not wipe out the skillet. Place 3 or 4 balls of beef (depends on the size of your skillet), and smash the burger into the hot skillet. You can mash with a wrapped large can, or two spatulas (press one over the other one). When the burger patty is flattened, season liberally with burger seasoning. The burger will hiss and sizzle while cooking, after about a minute or so you will want to flip over the burger patty. Top the patty with some additional seasoning and then the swiss cheese, cook for another 30 seconds or so and you will need to remove the patty from the grill.

Build the burger by spreading truffle mayonnaise onto both the top and bottom buns. Add the burger with cheese, then some of the mushrooms and onions, then the other burger with cheese, and top that with additional mushrooms and onions. Add the top bun.