To steep (macerate) the raisins in rum
Place 1 ½ cups raisins into a small, nonreactive saucepan and add the rum. Heat the liquid until it just starts to bubble, then turn off the heat, stir the contents and allow the raisins to macerate for 30 minutes to 1 hour (or longer). Drain and reserve the rum and raisins separately.
For the sponge
While the raisins steep, heat one cup milk with 2 tablespoons water and, when just warm to the touch, stir into a 2 ½ to 3 quart mixing bowl. Stir in the honey, and then sprinkle on the yeast. Let the yeast dissolve naturally for a few minutes. Once dissolved, add 2 cups bread flour and stir vigorously for 2 minutes, creating a mixture that is smooth and seemingly elastic—(stir briskly). Scrape down the sides of the bowl and cover the bowl with plastic wrap. Drape a clean kitchen towel over the top of the bowl and let it rest in a warm, draft-free spot for 1 hour.
For the dough
Using an electric mixer fitted with the paddle attachment, cream the softened butter with the sugar and salt. Beat the eggs and yolks with 1 teaspoon vanilla in a measuring cup (with a spout) using a fork. When the butter is light, add the beaten eggs a little at a time, beating well after each addition. While beating in the eggs, gently rewarm ½ cup of the reserved rum in a nonreactive saucepan. Add to the mixer bowl, the sour cream, warmed rum, citrus juice and zest and beat until combined (expect the mixture to look quite curdled at this point—this is fine). Turn the machine off and scrape down the bowl as necessary. Uncover the sponge and, after stirring it down, add the entire mixture to the mixer bowl. Turn the machine back on and combine well. Add 2 cups of bread flour and mix until smooth and glutinous. Add the drained raisins, the citron along with the candied cherries and beat again until incorporated. Add another cup of flour and beat it in well. Add one more cup of flour, this time in ½ cup increments, beating in each before adding the next. Beat again until well combined. Turn the machine off and scrape the dough from the paddle.
Finish the dough
Brush an 8 quart bowl with melted butter and set aside. Turn the dough out on to a floured surface and, with floured hands, knead the dough until smooth and somewhat elastic, adding only as much flour as you need. (You shouldn’t need more than 1 1/2 total after taking the bowl off the machine.) Use your scraper to remove the dough cleanly off the board, as you knead. (Expect the dough to always be quite moist.)
To rise the dough
Place the dough into the buttered bowl. Brush the top of the dough with melted butter and cover the bowl with well-greased plastic wrap and a clean towel. Place in a warm, draft-free spot to rise until billowy and almost double in bulk, about 3 hours.
About a second rise
You have a timing choice. Although you can shape the dough now, for the best, lightest, texture and a more developed flavor, punch the dough down, turn the dough over in the bowl and recover the dough to let it rise again for about 2 hours. If timing is an issue, either skip this second rise or punch down the dough and shape the dough as directed but allow it to rest in the refrigerator overnight (covered with a towel and then with a sheet of plastic wrap). The next morning, allow the dough to reach a billowy state, which can take several hours to accomplish.
To cut the dough
Place 2 nonstick paper panettone molds on a wire rack that fits inside a large shallow baking sheet. Uncover the dough and punch it down. Turn the dough out of the bowl and onto a very lightly floured work surface. Knead briefly and gently. Use a pastry scraper to divide the dough in half. Shape each half of the dough into a round and place the round into the paper mold (smoothest side up). In order to have the dough rise up and out of the paper molds, cut off a 1 generous inch off the top of the paper. The dough will be about 1 1/2 inches below the rim, initially. (Cutting the mold is not mandatory, just a choice and will determine how much of the baked panettone will be exposed.) Cover the dough loosely with plastic wrap that’s been generously sprayed with vegetable spray, then place a clean kitchen towel over the plastic and allow the shaped loaves to rise for 1 ½ to 2 hours, or until the dough is billowy and reaches ½ to 1 ½ inches above the top of the mold. (If you’ve skipped the second rise, for best texture, it’s especially important to allow the shaped dough to rise fully.)
To bake
Preheat the oven to 375F for 30 minutes before baking. Glaze the top of the risen dough with an egg wash made by mixing 1 egg with 1 tablespoon milk, 2 tablespoons reserved rum from soaking raisins and ¼ teaspoon vanilla—Strain this into another small bowl. (Depending on how long you’ve macerated the raisins, this will determine how much rum you will have reserved. If you don’t have enough, just add two more tablespoons rum to the glaze.) Bake the panettone in a preheated 375F oven until an internal temperature reaches between 190F and 195F when an instant thermometer is inserted deeply into the top center, 60 to 90 minutes. (After about 20 minutes, once golden, cover the loaves loosely with foil (shiny side up) and continue to bake this way. Bake uncovered for the last few minutes. Let cool completely on the wire rack. To slice, cut the loaf in half through the paper, then peel off the paper and place each half of the loaf (cut side down) on a cutting board. Cut into thin slices.
