In a large bowl mix together the beef mince with onion, salt, oregano, basil, garlic powder, black pepper, parmesan, breadcrumbs, egg and parsley. Mix together with your hands and roll into walnut sized meatballs.
In a non stick, oven proof pan and brown in oil and pour in the marinara sauce, stir and simmer for a few minutes to thicken.
Take off the heat and add the mozzarella, then a sheet of puff pastry that fits over the whole pan. With a small knife prick some holes, then bake for 30 mins until the top has puffed up and is golden.