To Make Sweet Shortcrust Pastry:

Add plain flour and sugar to a food processor and pulse to combine.
By hand: mix in a bowl until evenly combined.

Add cold diced butter and pulse until the mixture resembles fine breadcrumbs.
By hand: rub the butter into the flour and sugar until it forms breadcrumbs.

Add water or milk a tablespoon at a time and mix until a dough forms.

Form into a disc, wrap in cling film, and chill in the fridge for at least 15 minutes.

To Make Mince Pies:
5. Preheat oven to 180°C (160°C Fan) / 350°F / Gas Mark 4. Grease a mince pie tin.
6. Roll out chilled pastry on a lightly floured surface to 5mm thickness.
7. Cut out 7.4–7.5 cm rounds for the bases and press them into the tin.
8. Fill each base with 1 tbsp of mincemeat.
9. Cut lids using a 6–6.8 cm fluted cutter.
10. Brush edges with egg or milk and gently seal the lids on top.
11. Brush tops with egg or milk and sprinkle with demerara sugar if desired.
12. Bake for 20 minutes until golden.
13. Cool for at least 5 minutes, then dust with icing sugar and serve.