Make meatballs by combining mince, onion, carrot, parsley, breadcrumbs, feta, egg and salt and pepper in a bowl. Mix well.
Using clean hands, roll heaped tablespoonfuls of mixture into balls. Place flour on a large plate. Season with salt and pepper. Roll meatballs in flour to coat.
Heat 2 tablespoons oil in a non-stick frying pan over medium-high heat. Cook meatballs, in batches, for 2 minutes or until browned. Transfer to a plate.
Add remaining 1 tablespoon oil to a clean pan and heat over medium heat. Add onion and garlic. Cook, stirring occasionally, for 2 minutes or until onion is soft.
Add tomato paste and cook, stirring for 1 minute.
Add the tomatoes and stock to pan. Bring to the boil. Reduce heat to medium-low and simmer until sauce thickens slightly, 15-20 minutes.
Add meatballs to pan. Spoon sauce over them to coat. Cover and cook for 15 minutes or until meatballs are cooked through.
In the meantime, cook spaghetti in a large saucepan of boiling, salted water according to packet instructions. Drain.
Warm serving bowls, arrange spaghetti then spoon in meatballs and sauce. Top with Parmesan and basil leaves.