In a large bowl, gently mix together 2 pounds ground beef, 1 tablespoon Worcestershire sauce, 1 teaspoon seasoning salt, and 1 large beaten egg. Do not overmix.
Form the mixture into 4 patties. Refrigerate the patties while preparing the remaining ingredients.
Melt 1 tablespoon butter in a large skillet over medium-high heat.
Add 1 sliced onion and sauté for 3–4 minutes, stirring occasionally.
Stir in 8 ounces sliced mushrooms. Season with 1 teaspoon salt and ½ teaspoon pepper.
Sauté for another 3–4 minutes until the onions and mushrooms are softened and lightly browned. Remove from the pan and set aside.
Add the beef patties to the skillet and cook for 2–3 minutes per side until browned.
Transfer the patties to a baking dish and top each patty with the onion and mushroom mixture.
Bake for 8–10 minutes until the patties are cooked through.
Top each patty with 6 ounces shredded Monterey Jack cheese and bake for an additional 1–2 minutes until the cheese is melted.
Remove from the oven, serve warm and enjoy!
Video
Notes
Refrigerate the leftovers in an airtight container for up to 5 days.