Gently combine the ground beef, ground pork, beaten egg, Italian breadcrumbs, grated Parmesan, minced garlic, fresh parsley, salt, and pepper. Mix carefully without overworking the meat to keep the meatballs tender. Roll the mixture into ¾-inch meatballs.

Heat olive oil in a large soup pot over medium-high heat. Brown the meatballs in batches for about 2 minutes, turning to brown all sides. The meatballs will finish cooking in the soup. Remove browned meatballs and set aside.

In the same pot, add diced onions, carrots, and celery. Cook over medium heat for about 6 minutes until softened. Add a splash of olive oil if needed. Then add minced garlic and Italian seasoning and sauté for 1 more minute to release flavor.

Pour in the chicken broth and bring the mixture to a boil. Reduce heat to a gentle simmer. Add the browned meatballs back to the pot and let them cook gently in the simmering broth.

Boil the acini de pepe pasta in a separate pot until al dente, then drain. Cooking pasta separately prevents it from absorbing too much broth during storage.

Place the cooked pasta into individual serving bowls, then ladle the hot soup with meatballs and vegetables over the top. Stir fresh spinach into the soup and cook about 2 minutes until just wilted.

Sprinkle freshly grated Parmesan cheese on top of the soup in each bowl for added flavor and a savory finish. Serve immediately while hot.