PREPARING THE FILLING : Heat the olive oil in a large frypan and add the onions and cook for 5 minutes until soft now add the garlic and cook for a further 2 minutes , now add the mince , breaking the mince up , and cook over medium heat until mince is cooked through and browned , breaking up any lumps whilst cooking , next sprinkle the flour over the meat and stir through to combine , then add the beef stock , tomato paste , worcestershire sauce , salt and cracked black pepper to the pan and mix through well for a couple of minutes to combine all well , now bring to the boil then reduce heat slightly to simmer and simmer uncovered for 5 minutes or until mixture has reduced and thickened , then take off the heat and set aside to cool whilst you prepare pastry cases .