In a large bowl, combine the breadcrumbs and milk. Let them sit for 5 minutes so the breadcrumbs soften.

Add the eggs, grated cheese, garlic, onion, parsley, Italian seasoning, salt, black pepper, and crushed red pepper flakes if using. Mix until well combined.

Add the ground beef and ground pork. Using your hands, gently mix everything together until just combined. Do not overmix, or the meatballs can become tough.

Lightly coat your hands with olive oil and roll the mixture into medium-sized meatballs. Place them on a tray or cutting board while you prepare the sauce.

In a large heavy pot, heat the olive oil over medium heat. Add the diced onion and cook until softened. Stir in the garlic and cook for about 30 seconds, just until fragrant.

Add the tomato paste and stir for 1 to 2 minutes to deepen the flavor.

Pour in the crushed tomatoes and tomato puree or tomato sauce. Add the dried basil, oregano, crushed red pepper flakes if using, sugar if needed, salt, and black pepper. Stir well and bring the sauce to a gentle simmer.

Once the sauce is hot and gently bubbling, carefully lower the raw meatballs into the sauce one at a time. Do not stir right away, or the meatballs may break apart.

Cover the pot partially and let the meatballs cook gently in the sauce over low heat for 2 to 3 hours. Stir carefully once the meatballs have firmed up, moving them gently from the bottom so they do not stick.

Continue simmering until the sauce is rich, the meatballs are tender, and the house smells like Sunday dinner. The meatballs should be fully cooked through and reach 165°F / 74°C in the center.

Taste the sauce and adjust with more salt, pepper, basil, or cheese if needed.

Serve hot with pasta, ravioli, crusty bread, or on a large family-style platter with extra sauce spooned over the top.