Preheat the oven to 425°F (218°C).
In a large mixing bowl, combine the None Such Ready-to-Use Mincemeat, all-purpose flour, and granulated sugar. Mix well.
Cut the cold unsalted butter into small pieces and add it to the mixing bowl. Mix the ingredients with a pastry blender or your fingers until the mixture becomes crumbly.
Roll out one pie crust and transfer it to a 9-inch pie dish. Trim the excess dough from the edges.
Pour the mincemeat mixture into the pie crust and spread it out evenly.
Roll out the second pie crust and place it on top of the mincemeat mixture. Trim the excess dough and crimp the edges of the crusts together to seal the pie.
Cut a few small slits in the top of the pie crust to allow steam to escape during baking.
Brush the top of the pie with the lightly beaten egg white.
Place the pie on a baking sheet and bake for 20 minutes.
Reduce the oven temperature to 375°F (190°C) and bake for an additional 30-40 minutes, or until the crust is golden brown and the filling is bubbly.
Remove the pie from the oven and let it cool on a wire rack for at least 30 minutes before serving.