Blitz flour and cinnamon in a blender.
Add butter and pulse until the mixture resembles fine breadcrumbs.
Add almonds, sugar, egg yolk, and 45ml of water to form a soft dough.
Knead the dough briefly, wrap in film, and chill for 30 minutes.
Mix chopped marzipan, mincemeat, and sherry together in a bowl.
Preheat the oven to 190°C.
Roll out the pastry thinly and cut out twelve 7.5cm rounds.
Place rounds in a greased tart tin and fill with mincemeat mixture.
Cut out twelve stars and place one on top of each pie.
Bake for 20 minutes until the pastry is golden.
Transfer to a wire rack and sprinkle with caster sugar.