Pre-heat your oven to 200°c (180°c for fan-assisted ovens or Gas Mark 5) and grease a 12-hole tart/cupcake tray with a little butter.
First prep your mince meat - mincemeat straight from the jar is fine but adding some apple and cranberries gives your mince pies a little more interest. Peel, core and chop your apple into 1cm cubes and mix into the mincemeat. Add a handful of cranberries also. Set aside.
In a large bowl, cream the butter and sugar for the pastry, before adding the egg. Mix until combined before adding the flour and mixing to form a dough. Wrap the dough in cling film and place in the fridge to chill for about 30 minutes.
On a floured work surface, roll out the dough quite thin and cut circles large enough to line each hole in your tray. Gently place into your prepared tray, pressing the pastry into place.
Fill each pastry casing with mincemeat - enough to fill generously but not come over the top edge of your pastry casing.
In a medium bowl, cream the butter and icing sugar for the viennese paste, before adding the flour and cornflour, mixing to create a soft paste. Transfer the paste to a piping bag fitted with a large star nozzle.
Pipe the viennese paste from edge to centre of your filled mince pies, making a swirl on top.
Bake in your pre-heated oven for 20-30 minutes until a light golden colour on top. Allow to cool in tray for approx 15 minutes before transferring to a wire rack to cool completely.
Dust with a little icing sugar before serving.