Pan Sobao

Make the poolish in a small mixing bowl by stirring together the bread flour, water, and yeast. Cover the bowl with plastic wrap, and allow this to sit at room temperature for eight hours. After eight hours, transfer it to the fridge for an additional twenty-four hours (or until ready to make your bread). Do not allow to ferment longer than 24 hours.

An hour prior to mixing the bread dough, remove the poolish from the refrigerator and allow it to come to room temperature.

Remove the dough from the mixing bowl, lightly oil the bowl with a small amount of vegetable oil, and put the dough back into the bowl. Turn the dough over so the oiled surface is on top, then cover bowl with plastic film. Place the bowl into an in an unheated oven, or in a microwave. Allow the bread to ferment for one hour or until it's doubled in size with the door closed.

Punch down the dough after the fermentation time has elapsed to dispel the carbon dioxide that has developed in the dough. Fold the dough over itself, 3 or 4 times, to distribute the yeast and regulate the temperature of the dough. Invert the mixing bowl over the dough and allow it to relax for five minutes. 

While your dough is proofing, preheat your oven to 400°F. Place a cast iron skillet into the oven at the same time, placing it above, or beneath, an empty rack.