01 -
Preheat the oven to 350°F (175°C).
02 -
In a large bowl, combine ground beef, bread crumbs, egg, milk, onion, green pepper, mushrooms, Worcestershire sauce, garlic powder, salt, and pepper. Mix until well incorporated.
03 -
Press half of the meat mixture into the bottom of a loaf pan. Lay the provolone cheese slices over the meat, leaving a small border around the edges to prevent cheese from leaking out. Cover with the remaining meat mixture, pressing the edges to seal in the cheese.
04 -
In a small bowl, whisk together beef broth, ketchup, brown sugar, and mustard. Pour the sauce evenly over the meatloaf.
05 -
Bake in the preheated oven for 1 hour, or until the meatloaf is cooked through (internal temperature should reach 160°F/71°C).
06 -
Allow the meatloaf to rest for 10 minutes before slicing to serve.