To make the pastry, mix the flour and sieve into the bowl of a food processor.
Add the butter and blend until it is forms crumbs.
Add the cold water and mix to a dough and blend until it forms a ball.
Remove from the processor and chill for 30 minutes.
Pre-heat the oven to 180C/350F/Gas 4. Grease and flour your mince pie tins.
Remove the pastry from the fridge and roll out to a thickness of about 5mm. Cut the pastry in two groups of circles. The first with a cutter slightly larger than the size of each pie for the base and the second the same diameter as the pies for the lid. (the artistic among you might decide to cut some star shapes for the lids instead)
Line the mince pie tins with the larger circles, pushing the pastry up the edges and then spoon some mincemeat into each pie. Brush the edges of the smaller circles with the beaten egg, flip them over and press onto the top of each pie. Brush the pastry lids with the beaten egg so that they brown nicely in the oven.
Bake for around 20 minutes or until the pies are lightly browned and the pastry cooked.
Remove from the oven and sprinkle with sugar if desired. Cool slightly before carefully lifting them out of the tins (running a sharp knife round the edges to loosen them helps) and cooling on a rack.
When cold store in an airtight tin.