Combine 1 & 1/4 teaspoons of yeast with 1/3 cup of warm water and set aside until it becomes foamy.
Using the stand-mixer bowl, combine the starter from the night before with the yeast mixture and the remaining cup of water.
Use the mixer's flat beater to mix it evenly, then add 3 & 1/2 cups of flour.
Continue mixing until a dough starts forming; replace the flat beater with the dough hook and resume mixing until you get a smooth, soft dough.
Place dough into an oiled bowl, cover with a clean kitchen towel and set aside until it doubles in size.
Remove the dough from the bowl and transfer it on a flat surface (NOTE: Do not deflate the dough!)
Divide your pane Toscano dough into two portions.
Form each portion into a rectangle by folding the ends.
Place them on top of a generously floured baking tray lined with a baking sheet.
Use a sharp knife to make cuts on top of the dough.
Cover with the kitchen towel and set aside until it becomes (almost) double in size. It generally takes 45 to 60 minutes.
When the dough is almost ready, preheat your oven to 230°C (450°F).
Uncover the dough and place them in the middle of the oven.
After 15 minutes, open your oven and spray it with water three times.
Adjust the temperature to 200°C (375°F to 400° F) and bake for 30 to 35 more minutes.
Transfer your pane Toscano into a cooling rack to cool.
Slice, then serve.