2 pounds minced beef mix (or use 1½ pounds 85% lean ground beef plus ½ pound ground pork)
⅔ cup bread crumbs
¾ cupgrated Parmigiano-Reggiano
1 cup grated mozzarella
¾ cup marinara sauce, plus more for serving
Preheat the oven to 350°F and set an oven rack in the middle position. Line a baking sheet with aluminum foil and spray with nonstick cooking spray.
Place the onion, carrot, celery, and garlic in a food processor fitted with the steel blade and pulse until the vegetables are minced. (Alternatively, you can mince all of the vegetables by hand.)
In a bowl large enough to hold all of the ingredients, whisk the eggs with the basil, salt, pepper and balsamic vinegar.
Heat the oil in a medium skillet over medium heat. Add the minced vegetables and cook, stirring frequently, until softened, 5 to 7 minutes. Do not brown. Let cool until just warm.
Add the meat, bread crumbs, cheese, and cooked vegetables to the egg mixture and mix with your hands until evenly combined.
Form the meat mixture into a 9x5-inch loaf shape directly on the prepared baking sheet. Spread the marinara sauce evenly over top, letting it drip a bit down the sides.
Bake for 65 for 70 minutes. Let the meatloaf rest for about 10 minutes inside the oven. Add mozzarella and oregano on top while is resting. Scrape any fat away from the edges of the meatloaf , then use a wide spatula to transfer the meatloaf to a cutting board or serving platter. Slice and serve with more marinara sauce on the side, if desired.