In a large bowl, combine the ground beef (or turkey), grated Parmesan cheese, breadcrumbs, egg, garlic powder, onion powder, oregano, basil, salt, and pepper. Mix well and form small meatballs (about 1 inch in diameter).
In the slow cooker, add the chicken or vegetable broth, diced carrot, celery, and onion. Stir to combine.
Carefully add the meatballs to the slow cooker, ensuring they are submerged in the broth.
Cover and cook on low for 6-8 hours or on high for 3-4 hours.
About 30 minutes before serving, stir in the small pasta and chopped spinach. Adjust seasoning with salt and pepper if necessary.
Once the pasta is tender, serve the soup hot, garnished with fresh parsley and additional grated Parmesan if desired.
Notes
Serve the soup in individual bowls, topped with a generous sprinkle of Parmesan and a wedge of lemon for a fresh burst of flavor.