Ingredients:
Levain
51 gramsbread flour
51 gramswater
20 gramsripe sourdough starter
10 gramssuperfine or granulated sugar
Main Dough
65 gramsraisins
1/4 cupdark rum, plus more as needed
79 gramsunsalted butter
343 gramsbread flour, plus more as needed
165 gramswhole milk, divided
2 large eggs
21 gramssuperfine or granulated sugar
8 gramsfine sea salt
1/2 teaspoonvanilla extract
1/4 teaspoonalmond extract (optional)
1 tablespoonlemon zest (from about ½ large lemon)
Sliced almonds, for topping (optional)
Confectioners’ sugar, for topping (optional)
Directions:
Make the levain and soak the raisins (night before at 9:00 p.m.)
In the evening, when your sourdough starter is ripe (when you’d typically give it a refreshment), make the levain. In a large jar, combine 51 grams bread flour, 51 grams water, 20 grams ripe sourdough starter, and 10 grams sugar. Cover the jar loosely and let the levain ripen overnight at warm room temperature (I keep mine around 74°F to 76°F/23°C to 24°C). In a small bowl, combine the raisins and rum (use enough rum so they’re just covered). Cover the bowl.
Mix the dough (9:00 a.m.)
In the morning, your starter should be bubbly on top and at the sides, have risen in the jar, have a sour aroma, and have a loose consistency. If it was cold in your kitchen overnight or it isn’t displaying these signs, give it one more hour to rise and check again.
Cut 79 grams of butter into small pieces, place them on a plate, and set them aside to soften to room temperature. To the bowl of a stand mixer fitted with the dough hook attachment, add the 343 grams flour, 150 grams milk, 1 egg, 21 grams sugar, 8 grams salt, ½ teaspoon vanilla extract, ¼ teaspoon almond extract (if using), 1 tablespoon lemon zest, and the ripe levain. Set the mixer to low speed and mix until all the ingredients are combined and no dry bits of flour remain. Turn up the mixer to medium-low and mix for 3 to 5 minutes, until the dough starts to clump around the dough hook. This is a small amount of dough in the mixer, so if at any time the dough fails to effectively move around with the dough hook, you can switch to the paddle attachment. This is a moderately strong dough at this point, and should mostly pull away from the bottom of the mixing bowl.
Let the dough rest 10 minutes in the mixing bowl, uncovered.
The butter should be at room temperature by this time (meaning a finger should easily push into a piece with little resistance). If you used the paddle to mix, switch back to the dough hook, and with the mixer turned on to low speed, add the butter, one piece at a time, waiting to add the next until the previous is incorporated, 4 to 6 minutes total. Once all of the butter is added, turn the mixer up to medium-low and continue to mix until the dough smooths and once again begins clinging to the dough hook, 2 to 3 minutes. The dough will be cohesive, smooth, and elastic at the end of mixing.
Transfer the dough to another large container (or leave it in the mixing bowl) for bulk fermentation.
Bulk ferment the dough (9:30 a.m. to 1:30 p.m.)
Cover the dough with a reusable airtight cover and let it rise at warm room temperature (76°F/24°C) for a total of 4 hours. During this time, you’ll give the dough one set of “stretches and folds” (see next instruction for explanation) to give it additional strength.
To stretch and fold: 1 hour after the start of bulk fermentation, drain the raisins of any excess rum (discard the rum), then spread one-quarter (16 to 20 grams) of the raisins over the dough, pressing them gently into the dough to ensure they stick. Wet your hands, grab the north side (the side farthest from you) of the dough, and stretch it up and over to the south side. Spread another 16 grams of raisins over the top, then stretch the south side up to the north. Then, perform two more folds, one from east to west and one from west to east, adding the remaining 16 grams of raisins to the top of the dough before each. Finally, let the dough rest, covered, for the remaining 3 hours of bulk fermentation.
Shape the dough (1:30 p.m.)
Check your dough; after 4 hours, it should have risen about 30 percent in the bulk fermentation container, have a few scattered bubbles, be smoother with a slightly domed top, and be moderately light and fluffy to the touch. If the dough still looks sluggish or feels dense after 4 hours, give it another 30 minutes to rise in a warm spot, like your oven turned off with the light on inside (74 to 76°F/23 to 24°C).
Line the inside of an 8-inch round banneton or kitchen bowl with a clean kitchen towel and lightly dust with bread flour. Lightly flour the top of the dough and gently scrape it out to your work surface flour side down. Using a bench scraper and floured hand, flip the dough over and shape it into a very tight round by pushing and pulling the dough with the scraper against the work surface. Pushing and pulling will create tension on the top of the dough, creating a uniformly smooth surface.
Using your scraper, scoop up the dough, flip it over, and place it in the prepared banneton, seam side up. The seam on the bottom should be completely sealed. If it’s not, pinch the bottom closed with your fingers. Cover the banneton with a large plastic bag (or another bowl cover) and seal.
Proof the dough (1:45 p.m. to 4:45 p.m.)
Proof the dough at a warm temperature (74°F to 76°F/23°C to 24°C is ideal) for about 3 hours. If your kitchen is on the cool side, expect the dough to take longer to proof. Extend the proof time as necessary until the dough is puffy and a poke slowly springs back.
Bake and finish (4:45 p.m.)
Heat the oven to 400°F (200°C) with a rack in the middle and a baking stone on top (if you don’t have a baking stone, you can bake directly on a 13×18-inch half sheet pan ). In a small bowl, whisk together the remaining egg and 15 grams milk for the egg wash.
Place a piece of parchment paper on top of a pizza peel or upside-down sheet pan. Tip the proofed dough out to the center of the parchment paper so the seam is facing down.
Lightly brush the entire surface of the dough with the egg wash. Using a razor blade, baker’s lame, or sharp knife, make a cross shape with two shallow straight lines that intersect right at the top-center of the dough. Sprinkle on the sliced almonds (if using), slide the parchment paper onto the baking stone or sheet pan, and bake for 20 minutes. After 20 minutes, rotate the parchment paper halfway and reduce the oven to 350°F (175°C). Bake the mazanec for another 25 to 30 minutes, until it’s golden brown and the internal temperature is around 200°F (93°C). Remove from the oven and let cool completely on a wire rack.
If desired, fill a fine-meshed strainer with confectioners’ sugar and liberally dust the top of the mazanec. This is best the day it’s baked, but can be stored on the counter for 3 days, covered.