Gently mix turkey, breadcrumbs, egg, Parmesan, salt, and pepper in a bowl; form about 20-24 meatballs, 1-inch wide.
Heat oil in a large pot or Dutch oven over medium-high; brown meatballs on all sides about 5 minutes total and set aside. They need not be cooked through yet.
Cook onion in same pot 3 minutes until softened; add garlic and Italian seasoning and cook 1 more minute.
Stir in marinara and broth; bring to a boil.
Add pasta and return meatballs; reduce heat to medium and simmer 15 to 18 minutes, stirring occasionally, until pasta is tender and meatball centers reach 165°F (74°C).
Off heat, stand 3-5 minutes to thicken sauce.
Serve topped with shredded mozzarella and fresh basil.