Prepare the Patties:
In a bowl, combine the ground beef with Worcestershire sauce, salt, and pepper. Form the mixture into 4 equal-sized patties. Set aside.

Sauté the Mushrooms and Onions:
Heat the olive oil in a skillet over medium heat. Add the sliced onions and sauté for about 5 minutes, until softened and caramelized.
Add the sliced mushrooms to the skillet and cook for another 5-7 minutes, until the mushrooms release their moisture and become tender. Remove from the skillet and set aside.

Cook the Patties:
In the same skillet, cook the beef patties over medium heat for 4-5 minutes per side, or until they reach your desired level of doneness. Add a slice of Swiss cheese on top of each patty during the last minute of cooking to allow it to melt.

Assemble the Patty Melt:
Spread butter on one side of each slice of rye bread. Place a slice of bread, buttered side down, on a clean skillet over medium heat. Add a patty with melted Swiss cheese, a generous amount of sautéed mushrooms and onions, then top with another slice of buttered rye bread, buttered side up.
Grill each sandwich for 3-4 minutes per side, pressing down gently with a spatula, until the bread is golden brown and crispy.

Serve & Enjoy:
Once the patty melt is golden and crispy, remove from the skillet, slice, and serve immediately with pickles or a side of fries.