Melt the yeast in a small bowl with a little water. Dissolve salt and sugar in the milk.
In electric mixer, mix salt, flour, yeast and sugar at low speed and add 4 eggs.
The dough will quickly become smooth, then add 2 more eggs. Knead for 15 minutes at moderate speed.
Then add the softened butter, knead for 2 minutes.
Let the dough rise for 90 min at room temperature with the lid closed in a baking bowl, then punch it down again.
Repeat this procedure twice. Put the dough in the refrigerator for one night. Then the dough can be processed.