In a large bowl, rub the butter into the flour using your fingertips until it resembles fine breadcrumbs. Stir in the sugar, orange zest, and lemon zest.
Add the egg yolk and just enough cold water to bring the dough together. Wrap in cling film and chill for 30 minutes.
Preheat your oven to 400°F (200°C). Mix the mincemeat with the brandy or orange juice in a small bowl.
Roll out the pastry on a lightly floured surface to about ⅛-inch thick. Cut out 12 circles with a 3-inch cutter for the bases and 12 smaller circles or stars for the tops.
Press the larger circles into a 12-hole muffin tin. Spoon a generous teaspoon of mincemeat into each pastry case.
Top with the smaller pastry circles or stars, pressing the edges gently to seal. Brush with beaten egg and sprinkle with a little sugar.
Bake for 18-20 minutes until golden brown. Let them cool in the tin for 5 minutes, then transfer to a wire rack. Dust with icing sugar before serving if you like!
