Mix the yeast in lukewarm milk and let it rise. Stir the flour with the risen yeast, knead in the soft butter and the other ingredients and whip the dough. Place on a baking tray lined with parchment paper and enclose all around with pinched foil. Bake for about 1 hour at 180 °C.
The result is a flat cuboid, 5-7 cm thick. Wrap well in aluminum foil. Keeps a few weeks and gets better with time.