In a small saucepan, cover the potato pieces with plenty of water and bring to a boil. Cook until the pieces are very tender but not falling apart, about 15 minutes. Drain the potatoes and run through a food mill. Set aside and allow to cool.
Dissolve the yeast in the warm water. Place the flour on a clean work surface and make a large well in the center. Pour in the water and yeast mixture, the beaten eggs, and salt. Add the milled potato and pork fat, and begin to work these ingredients into the flour, bringing it all together to form a soft, sticky dough. Add more flour if necessary to bring it all together. Set aside in a clean bowl, cover with a damp towel, and let rise in a warm place for 1 hour.
Preheat the oven to 475 degrees F.
Place the loaves in bread pans or form them into rounds on baking sheets and bake for 35 to 40 minutes, until the bread is nicely browned on the outside. Let cool 10 minutes before slicing.
While the bread cools, return the citrus sauce to the heat and bring to a simmer. Add the segmented fruit, peel, and butter, and cook 10 minutes to thicken and heat through. Serve the sauce spooned over the bread.
Yield: 1 1/2 quarts