In a medium skillet over medium-high heat, cook the ground beef. Break up the meat as it browns, then add chopped onion and garlic. Cook until the onion is soft and translucent.

Season with salt and pepper. Stir in Worcestershire sauce and beef broth. Simmer until the mixture thickens and most of the liquid is absorbed.

Butter one side of each bread slice. Preheat a skillet or griddle over medium heat.

Place two slices of bread, butter side down, on the skillet. Add cheddar cheese, beef mixture, and mozzarella on top. Close with remaining bread slices, butter side up.

Cook 3–4 minutes per side, pressing gently, until golden brown and cheese is melted.

Slice in half, garnish with parsley, and serve hot.