Preheat the oven to 350°F (175°C).

Mix the ground beef, breadcrumbs, Parmesan cheese, prepared mac and cheese, minced garlic, onion powder, Italian seasoning, salt, and pepper in a large mixing bowl until well combined.

Whisk together the milk, ketchup, and egg in a separate bowl.

Fold the wet mixture gently into the meat mixture until just combined.

Shape the mixture into a loaf and transfer it into a lined loaf pan or form it on a baking sheet.

Spread a generous layer of ketchup over the top of the meatloaf.

Bake in the preheated oven for about 60 minutes, or until a meat thermometer reads 160°F (70°C).

Rest the meatloaf for about 10 minutes once out of the oven.

Serve it sliced and steaming hot.