1 Cook, peel, mash the potato: You will need 6-8 ounces of mashed potato for this potato bread recipe. That's between 3/4 cup and one cup of mashed potatoes.
The easiest way to cook the potato is to poke it all over with the tines of a fork and microwave it 4 minutes on one side, 4 minutes on the other side, on high. Let it cool, then peel it, and mash it with a fork.
Or, you can boil the potato. Peel the potato, cut it into large chunks, cover it with water in a pot, bring to a simmer, and cook for 10 minutes or so until a fork easily goes through the potatoes, drain, cool, and mash.
2 Heat the milk, whisk in mashed potato: Put two cups of milk into a medium saucepan with the salt and sugar. Heat on medium heat until the milk starts to bubble at the edges, then remove from heat. Stir to dissolve the salt and sugar. Whisk in the olive oil and the mashed potato.
Pour into the mixing bowl of a standing mixer (or just a large bowl if you don't have a mixer), and let cool until it is still warm, but not hot, to the touch. (If the mixture is too hot, it will kill the yeast in the next step.)
3 Add yeast and 2 cups of flour: Stir in the yeast. Stir in 2 cups (264 g) of the flour. Use a standing mixer such as a KitchenAid (recommended), attach the mixing paddle, and mix on medium high speed for 4 minutes. This will help break up any potato lumps and help incorporate the mashed potatoes into the dough.
(If you are using a bread machine, put the milk potato mixture, the yeast, and all of the flour into the bread machine and knead for 8 minutes, skip the next step and proceed to step 5.)
4 Add the remaining flour and knead: Swap out the mixing paddle for the dough hook on your mixer. Add the remaining 3 cups (416 g) of flour and mix on medium low speed for 8 minutes. The dough should be rather loose and a little tacky.
5 Put dough into a large bowl, let dough rise: Rub the inside of a large bowl with some olive oil. Transfer the dough from the mixing bowl and put it into this large bowl (can use your mixing bowl if you clean it, and coat the inside with oil). Gently coat the top of the dough with a little olive oil.
Cover the bowl with plastic wrap or a dampened towel (to prevent the dough from drying out). Place in a warm spot for 2 hours or in the refrigerator overnight.
The dough should at least double in size. You'll know when it has risen sufficiently when you press into the top with your fingertip and the indentation remains for a while.
6 Punch down the dough, place in loaf pans: Press down on the dough with your hand to deflate it. Turn it out onto a clean lightly floured surface and knead a couple of times. Cut the dough into two halves (a pastry scraper comes in handy for this).
Rub a little olive oil inside of two 8x4-inch loaf pans. Place a dough half in each and press the dough into the bottom of the pans.
7 Let dough rise again: Coat the top of the loaves with a little olive oil. Cover the loaf pans with plastic wrap and put in a warm place for 45 minutes to an hour or longer, until the dough has doubled in size.
8 Bake: Preheat oven to 350°F (175°C). Remove the plastic wrap from the loaf pans and gently place the loaf pans in the oven in the middle rack. Bake for 35 minutes until the crust is golden brown and the internal temperature is between 190 and 200°F.
While the bread is still warm in the pan, use a dull dinner knife and run along the edge of the pan between the pan and the bread to loosen the bread from the pan. Turn out of the loaf pans on to a rack, let cool completely before slicing.