Put the meat in a large saucepan and cook over a medium heat in its own fat until it starts to brown. Add the onion and cook for a further 5 minutes until softened. Add the stock and Worcestershire sauce. Simmer for 15-20 minutes.
Put the flour, cornflour and suet in a bowl, then gradually stir in the milk to form a thick batter. Put the meat in a 1.1 litre (2 pint) pie dish. Cover with the batter mixture. Bake for 30-35 minutes until risen and browned.