Preheat oven to 350°F. Line a large, rimmed baking sheet with foil. Set a wire rack in the baking sheet and cover the wire rack with foil. Poke holes in the foil (between the wires) so the meat juices can drip onto the rimmed baking sheet. Spray the foil with nonstick cooking spray.
In a large skillet set over medium heat, add the oil and onion. Cook for about 5-6 minutes, stirring often, until the onion is translucent and has softened.
2 tablespoons olive oil, 1 yellow onion
Add garlic and cook an additional 30 seconds until bloomed and fragrant. Remove from the heat.
2 cloves garlic
In a large mixing bowl, combine the eggs, breadcrumbs, parsley, basil oregano, salt, pepper, Parmesan and milk (or tomato sauce), and sautéed onion/garlic mixture. Mix until well combined.
4 large eggs, ⅔ cup Italian bread crumbs, 2 teaspoons dried parsley, 2 teaspoons dried basil, ½ teaspoon dried oregano, 1 teaspoon kosher salt, ½ teaspoon ground black pepper, ⅓ cup freshly grated Parmesan cheese, 3 tablespoons milk
Add the ground chuck and mix gently with a fork or clean hands until ingredients are incorporated. Add the mozzarella pearls and use your hands to gently combine (see note). Try not to over mix or the meatloaf will end up dense.
2 pounds ground chuck, 8 ounces Ciliegine mozzarella balls
Divide the mixture into 2 portions and form each portion into a loaf. Set the loaves on the wire rack of the prepared pan (about 3 inches apart) and cover each loaf with a thin layer of spaghetti sauce.
32 ounces spaghetti sauce
Set on the middle rack of the oven and bake at 350°F for 1 hour.
Spread an additional 2-3 tablespoons sauce over each loaf and bake an additional 20-30 minutes or until the internal temperature registers 160°F on an instant-read thermometer and the juices run clear.
Remove from the oven and let rest 15 minutes before cutting.
Serve on a bed of spaghetti and top with spaghetti sauce. Sprinkle with Parmesan cheese, shredded mozzarella and chopped parsley.
1 pound spaghetti, Freshly grated Parmesan cheese, Shredded mozzarella cheese, Chopped fresh parsley