The day before you want to make the cakes, place the milk and water in the small saucepan and heat to 30C/86F.
Transfer to the measuring jug, whisk in the yeast and teaspoon of sugar and leave to stand for 10 minutes to activate the yeast.
Sift the flour and salt into the large mixing bowl.
Add the sugar and stir in thoroughly.
Make a well in the centre of the dry ingredients and add the yeast mixture and softened butter.
Use your hands to bring everything together to a sticky dough.
Turn the dough out onto a lightly floured work surface and knead lightly for 5 minutes.
Push the dough down to form a flat rectangle that will fit into the baking tray or roasting tin.
Flour the bottom of the baking tray or roasting tin and place the flattened dough in it, cover with clingfilm and leave to prove for an hour or two or until the dough has doubled in size.
Place the dough in the fridge for an hour.
Place the cold butter block between two pieces of baking paper and gently pound with a rolling pin until square and flat (about 3mm thick).
Take the dough out of the fridge and place onto the lightly floured work surface.
Roll out to form a square.
Pull and roll each corner out so you have an envelope, 4 thin corners and a slightly raised centre piece.
Place the butter in the centre of the dough. Then pull in each corner to totally enclose the butter in the dough.
Roll the dough out carefully into a long rectangle shape.
Brush off any flour and fold the top third down to the centre, then the bottom third up and over that.
Cover with clingfilm and place back in the fridge for an hour.
Again, take the dough from the fridge onto the lightly floured surface, roll out to a long rectangle, fold into three and place in the fridge for another hour.
Repeat one more time and place on a lightly floured baking tray, cover and place in the fridge overnight (at least 12 hours).
Mix the dried fruit, sugar, spices and rum together in the small mixing bowl, cover with clingfilm and leave to steep overnight.