1. Make the meatballs: Preheat the oven to 350°F. Line a baking sheet with aluminum foil and set an oven-proof roasting rack over top. Spray the rack generously with nonstick cooking spray.
2. In a large bowl, beat the egg with the chives, sage and garlic. Add the remaining meatball ingredients and mash with your hands until evenly combined. Roll the mixture into tablespoon-size balls, about 1 inch in diameter (it will make approximately 50 meatballs), and place on the prepared rack. Bake for 15 to 18 minutes, or until lightly browned and cooked through. Set aside.
3. Meanwhile, start the soup. In a large soup pot or Dutch oven over medium heat, heat the olive oil. Add the onions, carrots, and celery and cook, stirring frequently, until the vegetables are softened, about 8 minutes. Add the chicken broth, beef broth, water, wine, bay leaf, salt and pepper and bring to a boil. Add the pasta and cook, uncovered, at a gentle boil until the pasta is al dente, 8 to 10 minutes (or according to package directions). Taste the soup and adjust the seasoning, if necessary. Reduce the heat to low and add the spinach and meatballs. Simmer for a few minutes, until the spinach is wilted and the meatballs are warmed through. Ladle into bowls and serve with grated Parmigiano Reggiano.
