Preheat your oven to 350°F, spray a 9x5 loaf pan with non-stick spray, and add a layer of parchment paper to the bottom allowing it to hang over the sides slightly.
In a small, heavy bottom skillet over medium heat, melt the butter and saute the onion for 2-3 minutes or until translucent. Add the garlic and cook until fragrant, about 30 seconds. Set aside.
In a large bowl, combine the sauteed onions, beef, breadcrumbs, eggs, BBQ sauce, Italian seasoning, salt and pepper. Mix very well using clean hands or a spatula.
Use ¾ of the beef mixture to line the inside of the loaf pan, leaving a deep crater in the center much like you would line a dish for a pie.
Fill the crater with half of mozzarella, then the mac and cheese, then top with mozzarella.
Use the remaining beef mixture to cover the loaf and pinch down the edges to seal in the mac and cheese.
Bake uncovered for 45 minutes.
In a small bowl combine the ketchup, sweet chili sauce and Dijon mustard.
Once the meatloaf is done, remove it from the oven and let it sit inside the pan for about 10 minutes. Loosen the edges with a knife if necessary and flip the pan over carefully on a serving plate and peel off the parchment.
Brush the top with the sauce, garnish with parsley and serve warm.