Melt the starter in the water in a small baking bowl. Add the flour and meanwhile knead until you get a soft smooth dough. Place this in a container and ferment, covered, for one night until the volume has quadrupled and the dough yields when lightly pressed.
Place polenta and water in a microwave-safe container and make on full wattage for 4 min. Stir and make repeatedly for 2 min. The mixture should be very thick. Alternatively, you can likewise make the polenta very thick in a small saucepan, stirring for about 5 min. Spread the polenta on a plate and cool for about 20 min.
Mix the wheat flour and gluten.
Pour the cold water into the baking bowl of the food processor form and add the flour mixture. Mix only briefly with the dough hook until just flat forms a rough dough, rest it for 15 min (autolysis).
Then knead the dough with the dough hook on medium speed for 15 min. until very smooth. Only then add the fermented steam and salt, continue mixing until the dough is firm and smooth. Next, add the polenta (solid in the meantime) in pieces and continue kneading until it is completely absorbed. The dough will now be much moister and stickier.
Transfer the dough directly from the bowl of the food processor to a large, lightly oiled baking dish and let rise for about 3 1/2 hours, until it is airy but has not yet doubled in volume. In