Make the pastry: Rub the butter into the flour until it looks like fine crumbs. Stir in the icing sugar and add the beaten egg. Mix lightly and form a dough. Chill for at least 30 minutes.
Roll and cut pastry: Roll dough on a floured surface to 3mm thick. Use a round cutter slightly bigger than your muffin tray holes to cut out bases. Press into tray.
Add filling: Spoon 1–2 teaspoons of mincemeat into each pastry base. Don’t overfill.
Add tops: Cut smaller circles or stars for tops and place them over the filling. Press edges gently to seal.
Glaze and bake: Brush tops with beaten egg. Bake at 200°C (180°C fan) for 15–20 minutes until golden.
Cool and serve: Let pies cool slightly. Dust with icing sugar. Serve warm or cold.