Slice the loaf of Italian bread lengthwise and place both halves on a baking sheet. Mix softened butter with garlic salt and spread it evenly on the bread. This step makes the base flavorful and ensures the bread bakes up golden and delicious.
Heat a skillet over medium heat and cook the ground beef with diced onion until the beef is browned and the onion is soft. Drain any excess grease. Stir in garlic powder, mustard, ketchup, water, salt, and pepper. Simmer until the sauce thickens and coats the meat.
Spread the sloppy joe filling evenly over the garlic bread halves. Make sure every bite will be loaded with filling. Top with shredded mozzarella and cheddar cheese for that irresistible melted topping.
Bake in a preheated oven at 350°F for 12–14 minutes until the cheese melts and bubbles. For a crispier finish, air fry at 400°F for 5 minutes instead.
Once baked, sprinkle fresh parsley over the bread. Slice into pieces and serve hot. The result is cheesy, garlicky, and absolutely satisfying.