Preheat oven to 375 degrees F (190 degrees C) and line a baking sheet or loaf pan with parchment paper.

In a large bowl, gently mix the ground beef, breadcrumbs, eggs, onion, parsley, salt, and pepper until combined.

Press two-thirds of the beef mixture into the bottom and sides of the loaf pan, creating a hollow well in the center.

Place the mozzarella cheese evenly into the hollow well of the meat.

Cover the cheese with the remaining one-third of the beef mixture, pinching the edges to seal completely so no cheese escapes.

Whisk the ketchup and brown sugar together in a small bowl, then brush the tomato-based glaze over the top of the loaf.

Bake for 55-60 minutes until the internal temperature of the beef reaches 160 degrees F. Roast the broccoli on a separate tray during the last 20 minutes.

Rest the baked loaf for 10 minutes before slicing to ensure the cheese sets.