In a bowl, mix the ground beef with Worcestershire sauce, salt, and pepper. Form into 4 oval-shaped patties to fit the bread slices.

Heat a skillet over medium-high heat and cook the patties for about 4-5 minutes per side or until they reach the desired doneness. Remove and set aside.

In a small bowl, combine mayonnaise, ketchup, mustard, relish, onion powder, garlic powder, and hot sauce (if using). Mix well until smooth. Set aside.

In the same skillet, reduce heat to medium and add a bit more butter or oil if needed. Add the sliced onions and cook, stirring occasionally, until caramelized and golden, about 15-20 minutes. Remove from heat.

Butter one side of each bread slice. Spread the special sauce on the non-buttered side of four slices.

On each of these slices, place a slice of cheese, a cooked patty, a portion of the caramelized onions, another slice of cheese, and finally top with another slice of bread (buttered side out).

Heat a clean skillet or griddle over medium heat.

Place the assembled sandwiches in the skillet, pressing them down slightly with a spatula. Cook until the bread is golden and crispy and the cheese has melted, about 3-4 minutes per side.

Once cooked, remove from the skillet, cut diagonally, and serve immediately.