To a mixing bowl, add the flour, potato flakes, dry milk powder and salt. Stir to mix well. To the yeast mixture, add the warm milk and mix well. Make a well in the flour mixture and add the yeast mixture and start mixing in the flour. When most of the flour has been mixed in, add the room temperature butter and continue mixing until a dough has formed. If necessary add additional water if needed. Turn the dough out onto a floured work surface and knead 8-15 minutes until the dough becomes a nice soft mass. Lightly oil a bowl, add the dough and turn over to coat with oil. Cover with a clean damp towel and set aside to raise. It should double in size in about an hour then proceed to shaping the loaf.