Combine the flour, sugar, yeast and salt in a large bowl and stir to combine.
475 g plain white flour or white bread flour, 40 g granulated sugar, 2 tsp instant yeast (easy-bake yeast), 1 tsp fine table salt
Mix the butter (or vegetable oil) into the mashed potato until smooth then stir in the lukewarm water. Pour all of this into the bowl of flour mixture and stir together to get a shaggy dough.
50 g vegan butter or vegetable oil, 240 g lukewarm water
Tip the contents of the bowl out onto a clean work surface and knead together, dusting lightly with flour as needed to prevent sticking - try to add as little flour as possible. You can alternatively use the 'slap & fold' method as explained in the blog post above the recipe. Knead for around 10 minutes until the dough passes the windowpane test (see notes).
Place the dough back into the bowl you used earlier. Drizzle a little oil on top and turn to coat. Cover the bowl with a clean bin bag and leave somewhere warm to rise for 1.5 to 2 hours, until doubled in volume.