Pat pork and beef chunks dry with paper towels, then season generously with salt and pepper.

Heat 2 tablespoons olive oil in a large heavy-bottomed pot over medium-high heat (about 375°F/190°C). Brown pork and beef on all sides, 3–4 minutes per side; transfer to a plate.

Reduce heat to medium. Add 3 tablespoons olive oil (or enough to coat the pot) and the chopped onion; cook 4–5 minutes until translucent.

Add minced garlic; cook 30 seconds until fragrant.

Stir in tomato paste and cook 2 minutes, stirring constantly, to caramelize.

Pour in whole peeled tomatoes with their juice, breaking them up with the spoon. Add sugar, salt, black pepper, oregano, red pepper flakes, and bay leaves. Return browned meats and any collected juices to the pot. Bring to a gentle simmer.

While sauce heats, combine ground beef, ground pork, breadcrumbs, Pecorino Romano, eggs, minced garlic, parsley, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a bowl. Mix gently until just combined.

Form mixture into 1.5-inch meatballs (about walnut size).

Heat 2 tablespoons olive oil in a large skillet over medium-high heat. Brown meatballs in batches, about 3 minutes per side; they do not need to cook through.

Add browned meatballs to the simmering sauce. Reduce heat to low; the sauce should barely bubble. Partially cover and cook 4–5 hours, stirring every 30 minutes to prevent sticking.

Five minutes before serving, stir in fresh basil. Taste and adjust seasoning with additional salt, pepper, or a pinch of sugar if necessary.