In a small bowl, combine the diced white bread and ⅔ cup of cold water. Let it soak for a few minutes, then mash it with a fork until it forms a paste-like consistency.

In a large mixing bowl, combine the mashed bread mixture, lean ground beef, sweet ground Italian sausage, grated Parmesan cheese, minced garlic, sea salt, black pepper, and egg.

Using your hands, gently combine the ingredients until they are just blended. Take care not to overmix, as this could result in tougher meatballs.

Use a small ice cream scoop or your hands to form meatballs, about 1½ inches in diameter, making approximately 22-23 meatballs.

Place the flour on a plate and lightly roll each meatball in the flour, shaking off any excess.

Heat 3 tablespoons of light olive oil in a large skillet over medium heat. In batches, sauté the meatballs, turning occasionally, until they are golden brown on all sides but not cooked through, about 5-7 minutes.

In the same skillet, add the chopped yellow onion and sauté for about 5 minutes, or until soft and translucent.

Pour in the crushed tomatoes and add the bay leaves (if using). Season with salt and pepper to taste.

Bring the sauce to a simmer and let it cook for 10 minutes, stirring occasionally.

Gently transfer the browned meatballs into the bubbling sauce. Lower the heat to a simmer, cover, and allow the meatballs to cook in the sauce for 30 to 40 minutes, or until they are fully cooked and the sauce has thickened a bit.

Add the minced basil to the sauce during the last 5 minutes of cooking and stir gently to combine.

While the meatballs are simmering, bring a large pot of salted water to a boil.

Drain the spaghetti and return it to the pot.

Serve the spaghetti topped with a generous ladle of sauce and a few meatballs.

Sprinkle with grated Parmesan cheese and serve with extra sauce on the side.