Meanwhile, grease and flour a 12cm x 20cm/5in x 8in bread tin. Turn the dough out onto a floured work surface again and knock back a few times. Divide equally into two pieces and shape into balls.
Once the potatoes are mashed, remove from the heat. To make the sandwiches, spread two of the garlic ciabatta slices with 1 tbsp softened butter each. Take one slice of the buttered garlic ...