To make the mincemeat, put all of the ingredients apart from the rum into a large saucepan.
Heat the mixture, allowing the butter to melt. Simmer the mixture very gently, stirring regularly, after 10 minutes remove the mincemeat from the heat.
Allow the mincemeat to cool completely then stir in the spiced rum or another alcohol of your choice like brandy.
The mincemeat will make more than you need for this recipe place the rest in sterilised jars. The mincemeat will keep for a few months, maturing the longer it is left. You can then use it in the rest of your Christmas baking.
The day before you want to eat the pastries, make the base dough by mixing the flour, sugar, salt, yeast, butter and milk in the bowl of a stand mixer fitted with the dough hook.
Mix on a low speed for 10 minutes, then increase the speed to medium and mix for a further 10 minutes.
Cover the dough and leave to rest for 10 minutes then tip onto a lightly floured work surface, flatten slightly and shape into a square, cover in cling film and refrigerate for 24 hours.
Take the 250g of butter and cover it in clingfilm, batter it with a rolling pin until it is approximately a 12cm square. Return the butter to the fridge and allow it to chill.
Take the dough out of the fridge and place it on a lightly floured surface, the dough may have risen slightly overnight, so flatten it down if necessary.
Roll out the pastry to a 25cm square that is 1cm thick, turn the dough so it looks like a diamond. Place the butter on the diamond of pastry so that it is square. Fold the pastry in to the middle so that it looks like an envelope and then use a rolling pin to flatten the dough down.
Then roll the pastry into a long rectangle, keep the work surface lightly floured and keep turning it when it has reached 22 x 40 cm fold up one end of the dough and then fold down the other end to encase it, like a letter. Return the dough to the fridge and let it chill for 30 mins.
Once the dough has chilled repeat the previous step and roll and fold the dough before returning it to the fridge.
Take the finished dough from the fridge and roll it out till it measures 30 x 40cm, neaten the edges and cut it into 12 x 10cm squares. Take one of the squares and make four 4cm diagonal cuts at each corner. Fold alternate points into the centre to create a pinwheel shape.
Take a heaped teaspoon of mincemeat and place it in the middle of the pinwheel.
Do this with the rest of the pinwheels and place them on a baking tray to prove. Cover the pastries with clingfilm and leave them to prove for 1-1hr 30mins until increased by half.
Preheat the oven to 210C/190C Fan/Gas Mark 6 brush the pastries all over with egg wash and bake for 10-15minutes until golden.
Leave the pastries to cool before mixing together the icing sugar and water and then drizzling or piping the icing over the finished pastries.