For the pre-dough, dissolve the yeast in 150 ml of water and stir in 200 g of flour. Let the dough rise in a warm place for 4 hours. At the end of this time, add the remaining water, salt and sugar. Stir in the butter. Gradually knead the flour into the dough. Let it rise again for 1.5 hours.
Take the yeast dough out of the bowl, shape it into a ball and let it rest for 5 minutes on a floured worktop. Then you cut it in two. Roll out half of the dough into a rectangle. Fold one of the long ends in the middle and place the other on top. Do the same with the second half of the dough and place both with the seam down on a baking sheet lined with baking paper. Make diagonal incisions with a knife. Cover the dough again and let rise for 40 minutes.
Preheat the oven to 200 °. Brush the bread with milk before baking. The baking time is approx. 20 minutes.