In a large bowl, combine the flour and shortening. Rub the two together until they combine to form a crumb consistency.
Add the sugar and 1 egg, and mix together until combined. Place the dough onto a lightly floured surface and knead it until the pastry comes together, but be careful not to over mix it or the pastry will become dense.
Wrap the dough in saran wrap and chill for 10 mins in the refrigerator.
Scoop the entire jar of mincemeat out into a medium-sized bowl and add the apples, mandarin oranges, and zest. Mix until thoroughly combined.
Preheat the oven to 425 °F. Roll out the dough to 3mm thick, or about the size of a typical men's wedding band.
Using a round cookie cutter with smooth edges about 6 inches in diameter, cut out 16 bases and tuck them into the wells of a muffin tin or tins. Put 1½ Tbsp mincemeat mixture into each. Brush the edge of each pie crust with a little beaten egg. Re-roll out the pastry to cut lids with a round cookie cutter with fluted edges about 2 1/2-3 inches in diameter and press them onto the pies and press down on the edges to seal them. Sprinkle the tops with the extra caster sugar.
Bake for 15-20 mins until golden brown. Leave to cool fully before releasing them from the muffin tin.
Once the mince pies are fully cooled, remove them from the muffin tin and dust them with a tad of powdered sugar
Just before you're ready to serve the mince pies, whip the heavy cream and powdered sugar on high for a few minutes until soft peaks form. Then, quickly fold in the brandy until combined, being careful not to be too vigorous or you will deflate the cream. Serve the mince pies with a dollop of brandy cream on top.