Soak - Combine bread pieces with ⅔ cup water and set aside for 5 minutes, then mash with a fork.

Mix - In a large mixing bowl or a stand mixer with paddle attachment, add: 1 lb ground beef, 1 lb sausage, ¼ cup parmesan, 4 minced garlic cloves, 1 tsp salt, ½ tsp black pepper, 1 egg, and mashed breadcrumbs. Mix until well combined.

Brown the meatballs - Form into 1 ½" meatballs (about a flat ice cream scoop of meat). Dredge/roll meatballs in flour, dusting off excess. Heat a deep, large, heavy skillet or a Dutch oven over medium heat with about 3 Tbsp oil. Add meatballs in 2 batches without crowding the pan and saute until browned on all sides (about 6 min total or 2 min per side). Remove meatballs and set aside (don't worry about cooking through at this point).

Saute onion - In the same skillet over medium heat, add more oil if needed and saute 1 cup chopped onion, stirring often until soft and golden (5 min). Add 4 cloves minced garlic and stir 1-2 minutes until fragrant.

Stir in crushed tomatoes and 2 bay leaves. Bring to a light boil (stir to make sure it's actually boiling and not just sending bubbles to the surface).

Add meatballs back into the pan with tomato sauce, partially cover and cook at a gentle simmer for 30 minutes, turning the meatballs occasionally. Meatballs will be tender, and the sauce will be thickened. A few minutes before the sauce is done, stir in chopped fresh basil and season with salt and pepper to taste. While meatballs simmer, make the pasta.

Cook pasta according to package instructions in salted water until al dente (or to desired doneness), drain, and return to the empty pot.

Toss together - Pour sauce and meatballs over spaghetti and toss gently to combine. To serve family-style, transfer to a large platter, garnish with parmesan cheese and fresh basil, and serve hot.