To make the stock, put the meat, whole onion, bay leaf and 2 litres of lightly salted cold water in a large saucepan. Cook over a very low heat for 1 hr 30 mins or until the beef shin is soft and falls apart easily – this can take up to 3 hrs. Skim off the scum with a spoon from time to time. Break up any larger pieces of beef into the broth, remove the whole onion and discard.