1. Make meatballs: Preheat oven to 350ºF. Mist a large, rimmed baking sheet with cooking spray. In a large bowl, combine meatball ingredients, mixing thoroughly with your hands. Roll mixture into 1-inch balls, moistening hands with water if mixture is sticky, and place in a single layer on baking sheet (make sure meatballs are not touching). Bake for 10 minutes, shaking sheet halfway through.
2. Make soup: In a large saucepan, bring broth to a simmer over high heat. Add meatballs, greens, 1 tsp. salt and 1/2 tsp. pepper. Cover, reduce heat to medium-low and simmer for 10 minutes. Stir in pasta; cook, uncovered, until pasta is tender, about 8 minutes, or as package label directs.
3. Season soup with salt and pepper. Ladle into bowls; sprinkle with grated Parmesan just before serving, if desired.