01 - In a large mixing bowl, gently mix ground turkey, breadcrumbs, egg, chopped parsley, minced garlic, grated onion, Parmesan, dried oregano, salt, and black pepper until just combined. Avoid overmixing.
02 - Roll the mixture into 16 golf ball-sized meatballs and arrange on a tray.
03 - Heat 2 tablespoons olive oil in a large skillet over medium heat. Brown meatballs in batches, turning frequently to brown all sides, about 5 minutes total. Transfer browned meatballs to a plate.
04 - In the same skillet, heat 2 tablespoons olive oil. Sauté the chopped onion until softened, 3 to 4 minutes. Add the minced garlic and cook for 1 minute more.
05 - Add crushed tomatoes, dried basil, dried oregano, sugar, salt, and pepper. Stir and bring to a gentle simmer.
06 - Nestle browned meatballs carefully into the sauce. Cover and simmer on low heat for 20 to 25 minutes until meatballs are fully cooked and sauce thickens. Stir in fresh basil leaves if desired.
07 - Serve the meatballs and marinara hot, accompanied by pasta, rice, or crusty bread.