Preheat a large skillet over medium heat for about 2 minutes. Add the ground beef and brown for approximately 4 minutes.

Add the finely diced onion and minced garlic to the skillet with the beef and stir for about 2-3 minutes until the onions soften.

Sprinkle in salt and black pepper, followed by the ketchup, mustard, and Worcestershire sauce. Let simmer for 1-2 minutes.

Spread softened butter on one side of each slice of bread for a crispy texture when grilled.

Lay out bread slices with the buttered side down, place cheddar cheese on each, add beef mixture and top with more cheese, then close with unbuttered slices.

Grill sandwiches in a clean skillet over medium-low heat for about 3-4 minutes per side until golden and melty.

Let the sandwiches rest for a minute, then cut in half and serve hot.