Combine the bread crumbs, egg, milk, and salt, stirring till everything is well moistened.
Add the ground meat, onion, cheese, and herbs. Mix gently till thoroughly combined.
Shape tiny meatballs, (about 1" diameter or less). Using a level teaspoon scoop (which volume-wise is actually 2 level measuring teaspoons) makes about the right size. Place the meatballs on a parchment-lined or lightly greased cookie sheet, and bake at 350F for approximately 20 minutes.
Get out a large pot, at least 6-quart capacity. Pour the olive oil into the bottom of the pot, and add the onions and carrots. Sauté, stirring frequently, until the onions are translucent and beginning to brown, about 10 minutes. Add the garlic, and cook for another couple of minutes.
Add the broth and herbs, bring to a simmer, and cook gently for 10 minutes.
Add the frozen chopped spinach, and simmer for 15 to 20 minutes.
Gently drop the meatballs into the soup. Simmer the soup for 30 minutes or so, then stir in the pasta, cooking till it's al dente. For orzo, this will take about 8 minutes or so.
Add salt and pepper to taste; using reduced-salt canned chicken broth, we added 1 teaspoon salt; and 1 teaspoon coarsely ground black pepper.
Serve the soup garnished with freshly grated Parmesan or Asiago cheese.