Combine breadcrumbs and milk in a large bowl, letting them soak for 2 minutes until the mixture resembles wet sand. Add ground beef, pork, egg, Parmesan, minced garlic, Italian seasoning, salt, and pepper. Gently mix with your hands just until combined—overmixing creates tough meatballs. Roll into 20-24 golf ball-sized portions, keeping them uniform for even cooking.

Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Brown meatballs in batches, turning them every 2-3 minutes until golden on all sides. Don't worry about cooking them through; they'll finish in the sauce. Transfer to a plate and set aside.

In the same pot, reduce heat to medium and sauté diced onion in the remaining oil for 3-4 minutes until softened and fragrant. Add minced garlic and cook for another 30 seconds until fragrant. Pour in crushed tomatoes, beef broth, dried basil, and red pepper flakes.

Nestle the browned meatballs back into the simmering sauce, spooning some liquid over the tops. Bring to a gentle boil, then reduce heat to medium-low. Cover and simmer for 15 minutes, allowing the meatballs to cook through while the sauce develops rich, concentrated flavors.

Stir in uncooked pasta, ensuring each piece is submerged in the liquid—add more broth if needed. Increase heat to medium and cook uncovered for 12-15 minutes, stirring occasionally to prevent sticking. Cook until pasta reaches al dente texture and the sauce clings to each piece.

Remove from heat when pasta reaches al dente texture and the sauce clings beautifully to each piece. Let it rest for 5 minutes to allow the starches to settle and the sauce to achieve perfect consistency. Serve garnished with fresh basil and extra Parmesan.