In a large bowl, gently combine the beef, egg, Parmesan, ≤ teaspoon salt, and the nutmeg.
In a small bowl, combine the bread crumbs and milk. Let stand until absorbed, about 3 minutes, and add to the beef.
Squeeze any excess water from the spinach, add to the beef, and mix gently.
Shape into 20 meatballs. Heat the oil in a large saucepan over medium heat.
Brown the meatballs, about 7 minutes.
Add the sauce and simmer for 6 minutes or until the meatballs are cooked through.