In a large bowl, combine the egg, ground beef, ground pork, bread crumbs, parmesan, fresh parsley, 3 minced garlic cloves, oregano, salt, and black pepper. Mix gently with your hands until just combined—overmixing will make the meatballs tough and dense. Once combined, roll the mixture into 1-inch meatballs (you should get about 24-30 meatballs). I like to wet my hands slightly with water as I form them to prevent sticking and create a smoother surface, which helps them brown more evenly.

Heat olive oil in a large pot over medium-high heat. Working in batches to avoid crowding, add the meatballs and brown them on all sides for 3-4 minutes total—they don't need to be fully cooked through at this stage, just develop a golden crust for flavor. Transfer the browned meatballs to a clean plate and set aside. I find that getting that initial sear creates much deeper flavor in the final soup.

In the same pot with the rendered fat and browned bits (don't clean it—that's flavor!), add the diced onion, carrots, and celery. Sauté for 10 minutes, stirring occasionally, until the vegetables begin to soften and the onions turn translucent. Then add the freshly minced garlic, salt, and black pepper, and cook for another 1 minute until fragrant. This aromatics base creates the foundation of the soup's flavor.

Pour the chicken broth into the pot with the sautéed vegetables and bring to a simmer. Return the browned meatballs to the pot—they'll finish cooking in the broth. Let everything simmer gently for about 10 minutes, which allows the meatballs to cook through and flavors to meld. The broth will also become slightly enriched from the meatballs.

Add the acini di pepe pasta to the simmering broth and cook for 10 minutes, stirring occasionally to prevent sticking. The pasta will absorb some of the broth and become tender. Check the pasta for doneness at the 10-minute mark—you want it al dente, not mushy.

Add the chopped spinach to the pot and stir until completely wilted, about 1-2 minutes. Taste and adjust seasoning with additional salt and pepper if needed. Ladle the soup into bowls and finish each serving with a generous handful of grated parmesan cheese. The warm spinach and pasta combined with those tender meatballs create a comforting, balanced dish.