Add 500 grams strong white bread flour, 150 grams floury potato (boiled, mashed and cooled, with no butter or milk), 7 grams fast action dried yeast, 30 grams caster sugar and 9 grams fine salt to a stand mixer bowl, keeping the salt and yeast on opposite sides. Add 1 large egg and 170 milliliters lukewarm whole milk, then mix on low with the dough hook until it comes together.