Kosher salt and freshly ground black pepper, to taste
1 tablespoon olive oil
Preheat oven to 375 degrees F. Lightly oil a 9×9 baking dish or coat with nonstick spray.
In a large bowl, combine beef, pork, egg, Panko, Parmesan, garlic powder, onion powder, allspice and nutmeg; season with salt and pepper, to taste. Using a wooden spoon or clean hands, stir until well combined. Roll the mixture into 1 1/4-to-1 1/2-inch meatballs, forming about 18-20 meatballs.
Heat olive oil in a large stockpot or Dutch oven over medium heat. Add meatballs, in batches, and cook until all sides are browned, about 2-3 minutes. Transfer to a paper towel-lined plate; set aside.
In a large pot of boiling salted water, cook pasta according to package instructions; drain well and stir in marinara sauce.
Add pasta to the prepared baking dish and top with meatballs; sprinkle with mozzarella. Place into oven and bake until bubbly and heated through, about 15-20 minutes.
Serve immediately, garnished with parsley, if desired.