In the morning, boil the potatoes until soft. Drain off liquid, saving 1 cup of the potato water for the bread. Mash the potatoes. Set aside for 30 minutes or until lukewarm.
In large bowl, mix mashed potatoes, potato water, water and yeast. Add sugar and salt. Stir. Add 3 cups of bread flour and mix well. Slowly add in remaining flour, enough flour to make a dough that follows the spoon around the bowl. Turn dough out onto lightly floured surface and knead for 8 minutes, adding more flour as needed until the dough is soft and smooth to the touch. Place dough in large greased bowl. Turn dough over in bowl so that the top is also lightly greased. Cover with clean cloth and let rise in warm, draft-free place for 1 hour or until doubled in size.
Punch down dough. Turn dough out onto lightly floured board and knead for 8 minutes or until the bubbles are out of the bread. Shape into a loaf of bread. Set loaf into greased 9 x 5-inch bread pan. Cover and let rise in warm, draft-free place for 45 minutes or until doubled in size.
Bake loaf at 350 degrees F for 55 minutes or until the bread is golden brown. Remove loaf from pan and let cool on rack.