Prep the carrots, celery and onions. Sauté them in the olive oil in a Dutch Oven or a similarly sized pot until onions are translucent. Add the garlic and saute another minute.
Add the 3 quarts of broth, pasta and meatballs; bring to a boil over medium heat.
Beat 2 large eggs with more Parmigiano-Reggiano cheese. Drizzle it slowly into the pot of soup, whisking vigorously until blended in completely.
Add in the spinach and reduce the heat to simmer for about 15 minutes
Adjust flavor lastly, adding salt and pepper to your taste preference. Since I used low- sodium broth, I did need to add about 2 teaspoons of Kosher salt and additional ground pepper. You may not need as much if you use other broth; add as needed.
Serve with additional Parmigiano-Reggiano cheese and some crusty bread. Yum!
Store leftovers promptly in the fridge.