3.

Transfer the potato mixture to the bowl of a stand mixer fitted with the paddle attachment (or use a hand mixer), add the flour, and mix on low until all of the potato mixture has been absorbed by the flour. Increase the speed to medium-high and beat until the dough appears smooth and elastic, about 30 seconds. Use a rubber spatula to scrape the dough into a clean bowl. Cover with plastic wrap and let it rise for 2 1/2 hours, until not quite doubled.