adapted from original at The Pioneer Woman
Preheat oven to 450°F. Line a rimmed sheet pan with foil to make cleanup easier.
Mix together the meats, breadcrumbs or Panko, Parmesan, egg, parsley, garlic, salt and pepper. Roughly portion meat into quarters and with each, roll 10 meatballs, a bit smaller than 1-inch in diameter, for a total of 40 meatballs. Bake for 8 minutes and broil for an additional 2 minutes, until browned and fully cooked (internal temp at least 160°). Set aside.
Heat oil in a soup pot. Add the onion, carrots, and celery and cook over medium heat, stirring now and then, until softened, about 5 minutes. Add the garlic and cook for a minute. Sprinkle in the salt and pepper.
Add the broths and bring to a boil. Add the pearl couscous or pasta, lower heat to maintain a simmer, and cook for 8 minutes, until couscous/pasta is just tender.
Add the spinach and simmer a minute to wilt. Add the cooked meatballs and simmer a couple minutes until warmed through. Remove from heat and stir in lemon juice. Top with parsley and/or other herby greens like lovage, sorrel, or Shiso, and shaved or grated Parmesan.