In a large bowl, combine the ground beef, ground pork, fresh breadcrumbs, grated Parmesan cheese, beaten egg, minced garlic, Italian seasoning, salt, and black pepper. Mix gently without overworking the mixture.

Divide the meat mixture into 8-10 equal portions, placing a mozzarella cube in the center of each portion. Wrap the mixture around the cheese, rolling into meatballs.

Heat olive oil in a large skillet over medium-high heat and add the meatballs, browning for about 2-3 minutes on each side.

Pour marinara sauce over the browned meatballs, lower the heat and simmer covered for 15-20 minutes or bake at 375°F for 15-18 minutes.

Bring salted water to a boil and cook spaghetti according to package instructions, then drain and toss with extra marinara sauce.

Serve the spaghetti in bowls topped with meatballs, additional marinara, and garnished with fresh basil and optional decorations.