In a large mixing bowl, combine ground beef, ground pork, fresh breadcrumbs, grated Parmesan cheese, egg, minced garlic, chopped parsley, Worcestershire sauce, dried oregano, paprika, salt, and pepper. Mix gently until just combined. Form into 1-inch meatballs and chill for at least 20 minutes.

Heat a large pot or Dutch oven over medium heat, add olive oil. Brown meatballs in batches to avoid overcrowding for about 2 minutes on each side until golden and crisp.

In the same pot, add more olive oil if needed, then sauté chopped onion, celery, carrots, and red bell pepper for about 5 minutes. Stir in minced garlic and cook for an additional minute.

Deglaze pot with chicken and beef broth, add bay leaf, Italian seasoning, and red pepper flakes. Bring to a boil then reduce heat to simmer. Return meatballs and let simmer for 10-12 minutes.

Stir in acini di pepe pasta and simmer for an additional 6-7 minutes until pasta is nearly al dente.

Remove bay leaf and fold in baby spinach until wilted. Adjust seasoning with salt or pepper as needed.

Ladle soup into bowls, top with fresh parsley and grated Parmesan cheese. Serve warm with crusty bread.