Wash, peel, cube, and boil the potato in plain unsalted water for about 12 minutes, or until tender.

Drain the potatoes over a bowl to catch the water. Measure out 11 oz of potato water and set aside to cool down.

Mash the potato (by itself without butter, milk or seasonings) and measure out the 6.5 oz (about 1 cup, slightly packed down.) Save the rest of the potato for another use.

Add all the ingredients for the dough (mashed potato, instant yeast, sugar, reserved cooking water, butter, oil, salt, and eggs) to the bowl of your stand mixer fitted with the paddle attachment.

Mix on low speed to incorporate all the ingredients.

Beat on medium low speed for 3 minutes.

Switch to the dough hook and knead on medium speed for 7-10 minutes, until the dough is very shiny, smooth, and stretchy. NOTE: The dough is pretty sticky, so a lot of it will remain stuck in the bottom of the bowl. The sides will mostly be clear of dough. When it’s ready, it should be pulling away from the sides of the bowl in sheets even thought it may still be sticking in the bottom.

Once smooth and supple, scrape the bowl down off the sides and into a compact round shape using an oiled spatula.

Spray the exposed dough with pan spray or brush with oil.

Cover the bowl with plastic wrap and refrigerate for at least 8 and up to 16 hours. The dough will be about doubled in size after refrigeration.

Remove the dough from the fridge and cut into two equal pieces. To be completely accurate, I weigh the whole amount of dough and divide by 2.

Press each piece firmly onto the counter to release as much of the trapped gases as you can. Shape into a rectangle—it doesn’t have to be perfect—of about 15” tall and 10” wide.

Starting from a short end, roll each half of the dough tightly into a log. Press from either end of the log to compact it so it will fit into a 9x5” bread pan.

Pan each log of dough in the same way and spray the tops with pan spray.

Cover and let rise at room temperature until the dough rises above the top of the pans by about an inch. This could take a long time since your dough is starting out refrigerated, so plan for at least 3-4 hours, depending on the temperature of your kitchen.

While the bread is rising, set a rack in the bottom third of your oven, and heat the oven to 350F.

When fully risen, bake the loaves for 30 minutes.

Rotate the loaves 180 degrees, tent with foil, and bake an additional 5-10 minutes, until the loaves reach 195-200F with an instant read thermometer. Loaves will be deeply golden brown.

Brush the tops of the loaves with the melted butter. This will make for a softer crust and lend a touch more richness.

Allow loaves to cool in the pans for 15 minutes then turn out onto a cooling rack to cool completely.