50g of strong flour (Manitoba)
5g of dried yeast
38g of water at room temperature

final dough:

60g of flour weak
115g strong flour (Manitoba)
1 egg yolk (about 30 g)
2 small eggs (80g)
17g butter, softened high quality
50g of powdered sugar
1 pinch of salt
pure vanilla extract
Final preparation:

125 g of butter quality
17 g of flour weak

Better if you start the night before to prepare the biga that should rise about 10 hours.
Mix the ingredients quickly, cover the bowl with cling film  and let rise in a warm place for at least 10 hours. The next morning start to prepare the pandoro dough.
Mix well the two flours and icing sugar with the biga. Add the eggs one at a time, then a pinch of salt and vanilla essence.When the dough appears smooth add the butter at room temperature. Knead until you have a smooth and elastic dough. Transfer the mixture into a large bowl and let rise until doubled in size.

Mix the butter with the flour and roll it into a very thin rectangle with a rolling pin. 
Store in the refrigerator wrapped in plastic wrap until ready to start making the folds.
Roll out the dough  with a rolling pin to obtain a rectangle with a 2cm thickness 
Put the butter in the center of the dough and fold the dough 3 times.
Roll out the dough with a rolling pin again and make fold again 3 times.. Practice this procedure for 3 times.
After you make each fold put the dough in the refrigerator for 20 minutes and 10 minutes in the freezer.
The butter must be cold.
At this point form a ball with the dough and arrange it, with the fold upwards, in the greased and floured pandoro mould .
Let rise until it reaches the edge of the mould.
Put it in not pre-heated oven to a temperature of 155 ยบ C for about 40 minutes. Do the toothpick test.
Let cool Pandoro in the mold.
Sprinkle with icing sugar before serving!