Preheat the oven to 200°C, fan 180°C, gas 6. Lightly dust the work surface with flour and lay the pastry flat, then roll it out to about the thickness of a 20p piece. Use the snowflake pastry cutter to stamp out 12 shapes. Push gently into the moulds of a fairy-cake tin, then place in the fridge for 10 minutes.
With the remaining pastry, which you may need to re-roll, cut out 12 stars with the other cutter.
In a bowl, mix together the mincemeat, white chocolate chips, cranberries and mixed peel. Spoon the mincemeat into the pastry cases, then top with a pastry star.
Brush the pastry with the egg yolk, sprinkle with the demerara sugar and bake in the oven for 15 minutes. Leave to cool a little, then serve lightly dusted with the icing sugar.