Make the filling by heating the oil in a medium pan, add the onion and fry gently until softened. Add the beef mince and cook, stirring frequently, until browned, then add the wine and tomato purée. Cover and simmer for 15 minutes or until the beef is cooked and the liquid is absorbed. Add the Worcestershire sauce and season to taste. Set aside and allow to cool. Preheat oven to gas 6, 200°C, fan 180°C. Unroll the pastry sheet and using a 5·5cm (21?4in) cutter, cut out 15 discs and use to line 15 mini muffin moulds. Then, using a 4·5cm (13?4 in) cutter cut out 15 discs for the lids from the remaining pastry. Crumble the Stilton into the cooled meat filling mixture, add the mustard and stir to combine. Divide the filling between the pastry cases, pressing down firmly. Brush the undersides of the lids with beaten egg and place one on top of each pie, pressing the edges together to seal. Make a small hole in the centre of each lid to allow the steam to escape. Brush the tops with beaten egg and bake for 15-18 minutes until the pastry is golden brown. Serve warm.