When blended creamy – pour into blender 4 cups additional water and blend till smooth.
Pour over raw potatoes and bake (covered) at 300 for 2 ½ hours. or 375 for 1 ½ hours. OR if you really want to be quick: par boil the potatoes, cook the white sauce till thick, pour it over the potatoes (lifting the slices so it is evenly distributed) and bake at 400 for 30 minutes.