In a large mixing bowl, combine hamburger, Italian sausage, bread crumbs, parsley, oregano, Parmesan, egg, salt and pepper with food-safe (vinyl or nitrile; powder-and latex-free) gloved hands.
Form mixture into small meatballs. (.3 oz each, about the width of a quarter)
Brown meatballs in a fry pan on medium heat, turning until browned on all sides; set aside.
In a stock pot, heat olive oil on medium heat.
Add carrots, celery, garlic; sauté until softened/wilted. (~10 min)
Add chicken stock, beef stock, and pasta to stock pot.
Bring to a boil; turn heat to low, cover, simmer ~10 minutes.
Stir in meatballs, simmer ~10 more minutes; stir in chopped spinach and simmer a few more minutes.