01 - Preheat your oven to 400°F. Grease a 9x13 inch baking dish with cooking spray or olive oil.
02 - In a large bowl, combine ground beef, Italian sausage, breadcrumbs, Parmesan cheese, egg, minced garlic, parsley, oregano, salt, and black pepper. Mix until just combined, then form into 1 inch balls.
03 - Heat a large skillet over medium-high heat with a splash of olive oil. Brown meatballs in batches for 5–6 minutes, turning to color all sides. Remove from skillet and set aside.
04 - Bring a large pot of salted water to boil. Cook pasta until al dente, 2 minutes less than package directions. Drain and set aside.
05 - In the same skillet, heat 2 tbsp olive oil over medium heat. Sauté onion until soft, about 5 minutes. Add garlic and cook for 1 minute. Stir in crushed tomatoes, tomato paste, dried basil, chili flakes, sugar, salt, and pepper. Simmer for 10 minutes until slightly thickened.
06 - Toss drained pasta with half the tomato sauce and transfer to prepared baking dish. Arrange browned meatballs over pasta, then pour remaining sauce over top.
07 - Sprinkle mozzarella and Parmesan cheese evenly over the meatballs and pasta.
08 - Bake for 25–30 minutes until cheese is golden and sauce is bubbling. Let rest for 5 minutes before serving. Garnish with fresh basil if desired.