In a medium-sized bowl, combine the ground chuck, Worcestershire sauce, seasoned salt, and ground black pepper and mix until well blended.
Shape mixture into 4 oblong portions about 1/2 inch thick.
Place the butter in a medium-sized skillet over medium-low heat. Place the sliced onions in the pan along with a two-finger pinch of salt. Sauté for 3 to 4 minutes, stirring occasionally.
Add the mushrooms to the skillet and sauté for another 3 to 4 minutes, or until the mushrooms begin to brown. Turn off the heat.
Heat a large cast-iron or stainless-steel skillet over medium heat. Place the seasoned burger patties in the skillet. Cook for 4 to 5 minutes, flip, and cook for another 3 to 4 minutes.
Top with the onions, mushrooms, and Monterey Jack cheese. Turn off the stove and serve when the cheese has melted.