Day 1: Prepare the starter by mixing warm water with yeast and set aside.
Day 1: Once yeast is ready, put in a stand mixer bowl with the dough hook and add flour and salt. Mix in low setting for 3 minutes and then increase in medium setting until the dough is smooth (no more than 7 minutes).
Day 1: Put the ball of dough in a greased container and place in a warm place for 3 hours. Punch the puffy dough and refrigerate overnight (at least 10 hours).
Day 1: Combine all the dried fruits, zests and the vin santo and leave in the refrigerator overnight.
Day 2: Take the starter out of the refrigerator two hours BEFORE preparing the panettone dough.
Day 2: Preheat the oven to 180 degrees Celsius (350 degrees F).
Day 2: Combine dry yeast with warm milk and set aside.
Day 2: Once the yeast is ready, combine with flour, vanilla, sugar, salt, cold milk and chilled egg yolks. Mix in a stand mixer in low speed for 3 minutes. Use the dough hook attachment in the mixer.
Day 2: Add the starter from Day 1 (see step #5) and mix for another 5 minutes. Stop the mixer and scrape the dough sticking on the sides of the bowl.
Day 2: Increase the setting of the mixer into medium and mix for 10 minutes, making sure to continuously scrape the sides of the bowl to avoid overheating the dough.
Day 2: Add softened butter and mix on low setting until completely smooth (usually around 10 minutes)
Day 2: Add the marinated dried fruit and mix until just combined.
Day 2: Cover the mixer bowl with a kitchen towel and set aside in a warm place until it has tripled in size. Mine took 4 hours.
Day 2: Pour the dough into your countertop. Do NOT use additional flour. Divide into two portions. Shape each portion into a ball and place each ball in a paper mold.
Day 2: Set aside in a warm place for two hours.
Day 2: Brush with egg-wash and bake for 35 to 45 minutes.
Day 2: Pierce the newly-baked panettone with two skewers or chopsticks and hang them upside down. This keeps the panettone from collapsing while it cools. Cool for at least two hours before serving, even better when served the following day.