Preheat the oven to 350 degrees Fahrenheit.

In a large bowl, gently mix together the ground beef, Worcestershire sauce, seasoning salt and egg.  Do not over mix.

Form the beef mixture into 4 patties.  Refrigerate the patties while you prepare the other ingredients.

Melt the butter in a large skillet over medium high heat.

Add the onions to the pan.  Sauté for 3-4 minutes, stirring occasionally.

Then stir in the sliced mushrooms.  Season the mixture with salt and pepper.

Sauté for 3-4 more minutes until the onions and mushrooms are soft and start to brown.  Remove the mixture from the pan to a separate plate.

Then add the beef patties to the pan and brown each sides of the patties (2-3 minutes per side).

Transfer the patties to a baking dish.  Top each patty with the mushroom and onion mixture.

Cook for 8-10 minutes until the patties are cooked through.

Top each patty with the shredded Monterey Jack Cheese.  Cook in the oven for 1-2 more minutes until the cheese is melted.

Remove from the oven, serve warm and enjoy!