Chef John's Holiday Panettone

The previous day, combine flour, cold water, and sourdough starter in a bowl. Allow the mixture to rest at room temperature for 8 hours or overnight.

At the same time, combine raisins, cherries, and pineapple in a separate bowl. Add rum to the mixture and let it soak, stirring occasionally, for 8 hours or overnight.

Combine warm water, yeast, and a pinch of sugar in a large bowl fitted with a dough hook attachment. Let the mixture sit for 10 minutes, allowing the yeast to dissolve. Add eggs, sugar, vanilla extract, orange zest, and lemon zest. Whisk the ingredients together until well combined. Add the panettone starter and incorporate it into the mixture. Gradually add flour and salt, kneading until the dough is smooth and elastic, approximately 10 minutes. Stop occasionally to scrape down the sides of the bowl if necessary. Add butter and continue kneading until it is fully incorporated into the dough, about 5 minutes. Transfer the dough to a work surface.

Using your fingers and a bench scraper, shape the dough into a rough ball. Return it to the bowl and cover it with plastic wrap. Allow the dough to rise until it has doubled in size, approximately 3 hours.

Transfer the dough back to your work surface and shape it into a rough ball. Place it in a resealable plastic bag and refrigerate for 8 hours or overnight.

Remove the dough from the bag and flatten it into a rectangle. Sprinkle with flour and roll out to at least 1/2-inch thickness. Spread the dried fruit evenly over the surface of the dough. Roll the dough into a log, sealing in the fruit. Roll both ends of the log towards the middle and smooth it over into a ball.

Place the dough ball in a short, wide panettone mold. Cover it with plastic wrap and allow it to rise until it has reached 2/3 of the way up the sides, approximately 3-4 hours.

Preheat your oven to 350 degrees F (175 degrees C). Mix egg and water together, then brush the mixture onto the top of the panettone. Cut 2 slits crosswise on top.

Bake the panettone in the preheated oven until it is beautifully browned, approximately 40-45 minutes. Poke 2 skewers through either side of the panettone and flip it over into a panettone hole or Dutch oven. Let it cool upside-down for 2 hours.

Remove the skewers and slice the panettone into pieces.