Start by slicing your mushrooms and onions.

Shape the ground beef into four equal patties and make a slight indentation in the center of each patty.

Heat olive oil in a large skillet over medium-high heat.

Add the patties to the skillet, season with salt and pepper, and cook for about 4-5 minutes on each side.

Remove the cooked patties and set aside. In the same skillet, add mushrooms and onions, cooking until they are tender and caramelized.

Place a slice of cheddar cheese on each patty, and return the patties to the skillet. Cover for a couple of minutes to melt the cheese.

Toast the hamburger buns on a baking sheet under the broiler.

Layer the sautéed mushrooms and onions on top of the cheese-covered patties and assemble on the toasted buns.