First, finely chop the onion and mince the garlic. Cook in the butter until soft, only a couple minutes.
In a small bowl, combine breadcrumbs and milk. This will form a kind of paste.
In a large mixing bowl, combine the ground beef, cooked onions and garlic, breadcrumbs and milk, eggs, 1 tablespoon ketchup, Italian seasoning, salt and pepper, 1 tablespoon chopped parsley and the Parmesan cheese. Stir to combine.
On a baking sheet lined with aluminum foil, form the loaf from the meatloaf batter. I use a loaf pan to do this. I press the mixture into the pan and then flip it over onto the baking sheet. A few taps and it’s out. But if you don’t want to dirty a loaf pan you can form the loaf by hand.
Bake at 350°F for 45 minutes.
In a small bowl, stir together the remaining ketchup, BBQ sauce and vinegar.
After the initial 45 minutes, remove the meatloaf from the oven and spread the sauce over the top. Bake for another 10-12 minutes. The meatloaf should reach an internal temperature of 160°F when done.
Allow the meatloaf to rest for at least 10 minutes before slicing into it. This allows the juices and fat from the meat to settle.