Gather all your ingredients, ensuring the onion is sliced thinly for optimal caramelization.

In a skillet over medium heat, add 1 tablespoon of butter. Once melted, add the sliced onions and cook until they turn a beautiful golden brown and caramelized, stirring occasionally (about 10-12 minutes).

While the onions are caramelizing, mix mayonnaise, ketchup, Dijon mustard, and Worcestershire sauce in a bowl. Blend until smooth and set aside.

Take your ground beef and form it into equally sized patties, seasoning each patty generously with salt and black pepper.

In the same skillet, add another tablespoon of butter and raise the heat to medium-high. Cook the patties for about 3-4 minutes on each side or until they reach your desired doneness.

Once the patties are cooked, place a slice of Swiss cheese on each patty and cover the skillet for a minute to allow the cheese to melt.

Spread the remaining butter on one side of each slice of rye bread. Toast the bread in a skillet until it’s crunchy and golden brown.

Spread the secret sauce on one side of each slice of toasted rye. Place a cheesy patty on one slice, followed by a spoonful of caramelized onions, and top it with another slice of bread.

Place the assembled sandwich back in the skillet. Grill for 2-3 minutes on each side until everything is heated through and the bread is crispy.

Slice the Patty Melt in half and serve warm with extra secret sauce on the side for dipping.