This meaty, as opposed to tomatoey, ragu makes the ideal filling for the Arancine and is perfect with pasta too. Longer-cooking and fattier minced (ground) beef will give you a better, richer flavour, as the sauce concentrates, but when time is short this version is perfectly fine. Estrattu is a rich, concentrated tomato paste which is very important in Sicilian cooking. Many people still make their own in summer with the abundance of cheap, ripe tomatoes. You will see mounds of it for sale in the markets. Do bring some home and use it in place of tomato purée, but it is salty so be careful with additional seasoning.