Soften unpeeled potatoes, drain, remove peel and mash finely (Petra: mash potatoes in a shallow bowl and steam well, then season lightly with salt).
Melt yeast in a little bit of the milk-water mixture.
Mix flour, salt and mashed potatoes in the baking bowl of a food processor. Add yeast and remaining liquid. Knead everything together into a smooth dough and let rise in a very large baking bowl with the lid on for about 2 hours*, until the dough has doubled in volume.
Knead dough lightly repeatedly and, covered with a wet dishcloth, rise another 30 minutes.
Pour bread dough into a buttered loaf pan, place in cold oven (middle rack) and bake at 220 °C (convection oven, 200 °C, gas, level 4) for about 45 min. until bread has a light brown crust.
Rias-Bucher: This potato bread, Arnoldo da Silva- Pereira told me, is typical pastry for the feasts of Saints Pedro, Antonio and Joao, which are celebrated in June and July. It is like a small carnival: in the evening, huge pyres are lit. Quadrilhas dance around the fire, often having practiced for months for the perfect synchronization of their movements.
The best and most colorful of the groups is awarded a prize.
Crust is nice and dark brown. I turned the loaves out of the molds after 40 min. and baked them standing freely for another 10 min. so that the sides also had a little bissc