Cut the butter into cubes and leave at room temperature to soften.
Coarsely chop the sultanas and currants.
Fit the Spiral dough tool to the machine.
Grease the loaf tin.
Add Ingredients 1 (flour, yeast, sugar, milk, egg, butter) into the Mixer bowl.
Attach the Mixer bowl to the machine and fit the splash guard.
Mix on speed 1 for 2 minutes.
Mix on speed 2 for 8 minutes.
Transfer the dough to the large glass bowl.
Retrieve, clean the Mixer bowl and fit the K beater.
Add Ingredients 2 (butter, mixed spice, sugar) into the Mixer bowl.
Mix on speed Max for 1 minute.
Scrape down the bowl.
Mix on speed Max for 30 seconds.
Carefully transfer the dough from the Mixer bowl to a lightly floured worksurface.
Roll out to a large rectangle about 2 mm thick.
Spread the butter and the sugar mixture over the surface of the dough.
Sprinkle Ingredients 3 (currents, sultanas) over the surface of the dough.
Roll the dough on its long side in a tight spiral to form a sausage shape.
Cut into equal pieces.
Place the dough into the loaf tin, cut side up.
Cover with a tea towel.
Leave to prove for 30 minutes.
Pre heat the oven to 180ºC.
Bake for 20 minutes at 180ºC.
Add Ingredients 4 (icing sugar, water) to the small bowl.
Mix until combined.
Spoon the icing over the buns whilst they are cooling.