Preheat oven to 400°F (200°C).
In a mixing bowl, combine ground beef, ground pork, grated Parmesan cheese, breadcrumbs, egg, minced garlic, chopped parsley, salt, and pepper. Mix thoroughly and form into small meatballs, about 1 inch in diameter.
Place meatballs on a baking sheet and bake in the preheated oven for 20 minutes until browned and cooked through.
While the meatballs are baking, heat a large pot over medium heat. Add diced onion, sliced carrots, and sliced celery, sautéing for about 5 minutes until softened.
Pour in the chicken broth and bring to a boil.
Once boiling, add the small pasta and cook according to package instructions (about 8-10 minutes) until tender.
Lower the heat; add the baked meatballs and chopped spinach or escarole to the pot. Simmer for an additional 5 minutes until the greens have wilted.
Season the soup with salt and pepper to taste.
Serve hot, garnished with lemon wedges if desired.