Submerge the bread entirely in cold water and let it sit for 5 to 6 minutes or until soaked and soft.
Next, squeeze as much water from the bread as possible.
Add it to a large bowl with the ground beef, ground pork, grated cheese, ½ cup onion, 2 minced garlic cloves, 2 tablespoons minced basil, 2 eggs, salt and pepper.
Mix thoroughly until combined. Test the flavors of everything but frying a small piece. Adjust the seasonings accordingly.
Form 12 equally-sized meatballs and set them to the side.
Add 2 tablespoons of olive oil to a large pot over medium heat. Add in the 1 cup of onions, gently season, and sauté for 5 minutes.
Turn the heat down to low and cook them for 10 minutes while occasionally stirring. Then, stir in the garlic and cook it just until it becomes fragrant, which only takes 30 to 45 seconds.
Deglaze with the red wine and cook over medium heat until only 2 to 3 tablespoons remain.
Pour in the tomato puree along with water.
Place in the fresh basil leaves, bay leaf, and salt and cook over low to medium heat for 15 to 20 minutes to help reduce and concentrate the flavors.
Finish by stirring the balsamic vinegar. Set aside and keep warm.
In a large non-stick frying pan over medium to medium-high heat with 2 tablespoons of oil, fry the meatballs on all sides until browned. This takes about 2 to 3 minutes per side. They do not need to be cooked all the way through.
Next, add them to the pot with sauce and cook over low heat for an additional 15 to 20 minutes or until the meatballs are cooked throughout.
In a large pot of boiling salted water, cook the spaghetti until al dente.
Drain the pasta and add in to a large bowl, along with several ladles of the meatball sauce.
Serve the tomato sauce-coated pasta with several meatballs on top. Garnish with optional additional grated cheese and fresh basil.
Notes
Make-Ahead: You can make this up to 2 days before serving it. Keep it in the refrigerator until 1 hour before serving. Reheat the sauce and meatballs in a large pot, and boil the pasta separately. Combine everything, and then serve.How to Store: Cover and refrigerate for 5 days. It will also freeze, covered, for up to 3 months. If possible, keep the meatballs and sauce separate from the pasta. Thaw for 1 day before reheating.How to Reheat: Add your desired amount to a medium-size pot with 2 to 3 tablespoons of water and cook over low heat until hot. You can also reheat in a microwave-safe bowl until hot.Substitute the fresh basil in the sauce for 2 teaspoons of dryUse 1 tablespoon of dry basil instead of the fresh basil for the meatballs.For the meatballs, substitute 2 teaspoons of dry onion granules or powder for fresh and 1 teaspoon of dry garlic granules or powder for fresh.Al dente means to the tooth. The pasta should be firm but not crunchy.