Heat olive oil in a large soup pot over medium heat. Add onions, season with salt and pepper, then saute for 3-4 minutes or until translucent Add garlic then saute for 30 more seconds. Add frozen spinach then stir to break up. Add chicken broth then bring to a boil. Once boiling add pasta and meatballs then cook until pasta is al dente, about 8-9 minutes. In a separate bowl, whisk together eggs and parmesan cheese. Drizzle into soup while stirring constantly then cook for 1 more minute before serving.