Boil the potato until well done. Peel and finely mash it, adding a little cold water to soften. Stir the brown sugar and lard into it. Add the hop yeast. Mix the ingredients through and through. Put the sponge in a mug with a close fitting top. Let it stand for several hours to rise up.

Add salt to the flour. Sift into the tray. Pour in the sponge. Add enough cold water to the flour to work it up into a rather stiff dough. Knead it until the dough is smooth. Let it stand all night to rise up.

Work it over in the morning, using just enough flour to keep it from sticking to the hands. Use a little lard on the hands when making out the loaf as it keeps the crust from being too hard. Allow an hour to rise up before baking. Bake in a oven heated to 350F at 350°F for about an hour. It should be thoroughly done and well dried.