In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic, salt, black pepper, onion powder, and Italian seasoning. Mix until well combined.
Shape the mixture into meatballs, placing a cube of mozzarella cheese in the center of each.
Heat olive oil in an oven-safe skillet over medium heat. Brown the meatballs on all sides for 5-7 minutes.
In the same skillet, add beef broth, stout beer, and Worcestershire sauce. Stir and bring to a simmer.
Return the browned meatballs to the skillet, cover, and bake in the oven for 20 minutes.