Preheat your oven to 375°F (190°C) and prepare a baking sheet or a loaf pan by greasing it.

Mix together ground beef, breadcrumbs, eggs, milk, onion, garlic, Worcestershire sauce, tomato paste, salt, pepper, oregano, and basil in a large mixing bowl.

Form half the mixture into a loaf, make a trench in the center, fill with mozzarella, then cover with remaining mixture.

Whisk ketchup, brown sugar, and balsamic vinegar in a bowl and brush over meatloaf.

Bake for 50-60 minutes or until the internal temperature reaches 160°F (71°C).

Let the meatloaf rest for 10 minutes before slicing and serving.