01 -
Preheat the oven to 375°F (190°C).
02 -
In a large bowl, combine ground beef, sausage, onion, garlic, breadcrumbs, eggs, Parmesan cheese, Italian seasoning, and parsley. Add milk, salt, and pepper, then mix everything together until fully combined.
03 -
On a baking sheet, form the meat mixture into a rectangular loaf (about 9×12 inches). Create a well in the center of the meatloaf and stuff it with mozzarella cheese, spinach (if using), and a spoonful of marinara sauce. Carefully fold the meat around the filling, sealing the edges to form a loaf.
04 -
Spread the remaining marinara sauce on top of the meatloaf and sprinkle with Parmesan cheese.
05 -
Bake for 45-55 minutes, or until the internal temperature reaches 160°F.
06 -
Let the meatloaf rest for 10 minutes before slicing. Serve with extra marinara sauce on the side.