Plain mashed potatoes create a fantastic breakfast bread, just made for butter and jam. If you prefer your spuds enhanced with garlic, chives, blue cheese, or bacon, this recipe will give you a more flavorful bread, great for leftover turkey sandwiches.
In a saucepan, melt butter in milk. Let cool to room temperature.
In the bowl of a stand mixer with dough hook, combine milk mixture with mashed potatoes, salt, sugar, yeast, warm water, and flour and knead with dough hook for about 5 minutes, until you have a smooth and slightly glossy dough. Place into an oiled bowl. Cover with plastic or a clean, dry dish towel and let rise until doubled in size, about 1 hour.
Oil two 9x5-inch loaf pans.
Turn dough out onto a lightly floured work surface. Divide in half and knead three or four times. Shape each portion into a rectangle, about 9 inches long. Roll each one lengthwise into a log and place seam side down into its own loaf pan. Cover with plastic or a clean, dry dish towel and let rise until doubled in bulk, about 1 hour.
Preheat oven to 375ºF.
Bake for 30 minutes, or until loaves sound hollow when tapped. Turn onto wire racks and let cool completely.