Cut the shortening and butter into cubes with a blunt knife or pastry cutter. Rub into the flour until the mixture resembles fine crumb, (you can do this in a food processor) then stir in the sugar
Separate the egg and mix the yolk with the cold water set aside the white.
Add the egg to the flour and work the mixture together with a knife until it comes together, knead briefly. Wrap in clingfilm and refrigerate for 30 minutes.
Pre-heat the oven to 190C/170C Fan/Gas 5
Cut off 1/3 of the pastry and put it to one side. Roll out the larger piece of pastry and use to line an 18cm flan/quiche tin.
Mix the brandy or Tia Maria (if using) with the mincemeat. Fill the pastry case with mincemeat. Then roll out the remaining pastry to make a lid.
Brush the edges of the pastry base with egg white and place on the lid, trim off excess pastry pressing the edges of the pastry together.
Brush the top of the pastry with egg white and sprinkle with flaked almonds.
Bake 35-40 minutes, or until golden and crisp. Leave for about 10 minutes to cool, then dust with icing sugar.
Notes
If using shop-bought mincemeat, add a tablespoon of brandy or Tia Maria along with 50g of chopped dark chocolate or small chocolate chips, stir thoroughly.