In a large mixing bowl, gently combine the ground beef, ground pork, beaten egg, breadcrumbs, Parmesan cheese, minced garlic, parsley, salt, and black pepper. Mix until just combined—do not overwork the mixture. Roll the mixture into small meatballs, approximately ¾-inch in diameter, and set aside.

Heat olive oil in a large soup pot over medium-high heat. Working in batches, brown the meatballs for approximately 2 minutes, turning occasionally to sear the exterior. The meatballs will not cook through at this stage, as they will finish cooking in the soup. Remove the browned meatballs and set aside.

In the same pot, add the diced onion, carrots, and celery. Sauté over medium heat for approximately 6 minutes, stirring occasionally, until the vegetables are softened. Add a small amount of olive oil if needed during cooking.

Stir in the minced garlic and Italian seasoning, cooking for 1 minute until aromatic. Pour in the chicken broth, stirring to combine. Increase the heat to bring the soup to a boil, then reduce to a simmer.

Gently add the browned meatballs back into the soup. Allow the soup to simmer gently for 15–20 minutes, ensuring the meatballs are fully cooked and the flavors meld together.

In a separate pot, cook the acini de pepe pasta according to the package instructions until al dente. Drain and set aside. Keeping the pasta separate prevents it from absorbing too much broth during storage.

Stir the fresh spinach into the soup and cook for 2 minutes, or until wilted. Taste the soup and adjust the seasoning with additional salt and black pepper as needed.

To serve, add a portion of the cooked pasta to individual bowls. Ladle the soup over the pasta and garnish with freshly grated Parmesan cheese. Serve hot.