In a large skillet over medium heat, add the ground beef. Break it apart with a spatula and cook for about 4 minutes, stirring frequently, until browned and no longer pink.

Stir in the finely diced onion and minced garlic, continuing to cook for about 2-3 minutes until the onion becomes translucent and fragrant.

Mix in salt, pepper, ketchup, mustard, and Worcestershire sauce. Let the mixture simmer for 1-2 minutes.

Spread softened butter generously on one side of each slice of bread.

Layer by placing one slice of buttered bread, followed by a layer of cheese, then the savory beef mixture, and another layer of cheese, topping with a second slice of buttered bread.

In the same skillet, grill the assembled sandwich over medium-low heat for about 3-4 minutes on each side.

Remove the sandwich from the skillet and let it rest for a minute before slicing.