For the pastry:
Combine the flour, sugar and salt together. Add the oil and blend in using a pastry cutter, electric beaters or a mixer fitted with the paddle attachment, until the flour looks evenly crumbly in texture.
Add the butter and cut in until rough and crumbly but small pieces of butter are still visible. Stir the water and vinegar (or lemon juice, if using) together and add all at once to the flour mixture, mixing just until the dough comes together. Shape the dough into 2 disks, wrap and chill until firm, at least an hour.
The dough can be made up to 2 days ahead and stored chilled, or can be frozen for up to 3 months, thawing in the fridge before rolling.
For the mincemeat filling:
Toss the grated apple, raisins, currants, dried cranberries and candied ginger with the brown sugar, honey, brandy, lemon juice, orange and lemon zests and spices. Cover and chill for at least 2 hours, up to 24 hours.
Preheat the oven to 400 F. Pull out the dough from the fridge 15-30 minutes before rolling. On a lightly floured surface, roll out the first disk of dough into a circle just less than ¼-inch thick. Dust a 9-inch pie plate with flour and line the plate with the pastry. Trim away the excess dough and pinch the edges to create a fluted design.
Stir the melted butter into the mincemeat filling and spoon this into the pie shell, spreading to level it. Roll out the second disk of dough and use a cookie cutter to cut out shapes of your choosing. Arrange the cut-outs over the mincemeat filling, placing them closely together over the entire surface of the pie. Brush the pastry with eggwash and sprinkle lightly with sugar.
Place the pie onto a parchment-lined baking tray and bake for 10 minutes at 400 F, then reduce the oven temperature to 375 F and then bake for about another 40 minutes, until the crust is golden brown. Cool the pie for at least 2 hours before slicing, or cool to room temperature and then chill before serving.