In a bowl, mix the sultanas with all of the other ingredients up to and including the rum, cover and leave to steep in the fridge for approx. 12 hrs. or overnight.
Mix the flour and salt in a bowl. Add the butter and rub together using your hands to form an even, crumbly mixture. Pour in the water and mix quickly to form a soft, smooth dough; do not knead. Flatten the dough, cover and chill for approx. 30 mins.
On a lightly floured surface, roll out the dough to approx. 3 mm thick, cut out 24 circles (each approx. 7 cm in diameter), place in the prepared tins. Spoon approx. 1 tbsp of filling into each. Cut 24 stars out of the remaining dough, place these on top of the filling, brush with egg yolk, sprinkle with sugar.
Approx. 20 mins. in the centre of an oven preheated to 220°C. Remove from the oven, allow to cool slightly, remove the mince pies from the tins and leave to cool on a rack.