Place the dough from the first rising into the mixer.
Add the flour and begin mixing using the paddle.
This recipe yields three 1/2 kg panettone. Let's face it, if you're spending a day to bake a panettone it's well worth it to bake three at the same time. Panettone make wonderful holiday gifts so it's great to have a few extra on hand. They also freeze well. Begin by assembling all of your ingredients, and then divide them up by what you will need for each step and dough rising.
A few comments on the ingredients and procedure.
For the all-purpose flour I strongly suggest that you use a high-quality flour such as King Arthur.
Italian flour is classified quite differently from American flour and a classic Italian panettone recipe would call for a strong, or gluten rich, flour such as Manitoba flour or W380 flour. If you have access to either of these flour types by all means use them in place of all-purpose flour.
I like panettone made with dried cranberries that have been soaked the night before in rum. If you want to stick to a classic recipe then you should use the Sultana raisins and candied citrus fruit. Feel free to add your own flavor twist to the panettone: try adding mini chocolate chips, crumbled chestnuts or pine nuts.
I strongly suggest you use a fresh brewers yeast rather than a packaged dry yeast for panettone. If you happen to have a good mother yeast on hand by all means use that in place of the brewers yeast.
Egg amounts are indicated in grams as this is the most precise way to measure ingredients for baking. Eggs can differ in size, and therefore weight, but an average large U.S. egg weighs roughly 50 g out of the shell, and about 1/3 of this is yolk. Next to the egg weight in the ingredients list I have indicated the approximate number of eggs required, assuming an egg weight of 50 g.
To facilitate the speed of dough risings you should rise the dough in an unheated oven with the oven light on, or a warm spot in your kitchen. The dough will rise best if the room is about 80°F.