Step 1

(10:00 a.m.)In a medium jar mix together the Levain ingredients. Cover the jar and keep it at a warm temperature for 3-hours.

Step 2

(1:00 p.m.)To the bowl of a stand mixer fitted with the dough hook attachment, add the flour, milk, egg, half of the sugar, salt, and levain. Mix on low speed until incorporated and let rest, uncovered, for 10 minutes. Turn the mixer up to medium speed and mix for 5 minutes until the dough pulls from the sides of the mixing bowl. Stream in the remaining sugar while the mixer is running and mix for another 1 to 2 minutes until the dough comes back together. While continuing to mix, add the butter, one pat at a time. Mix for another few minutes until the dough smooths out and clings to the dough hook. Transfer the dough to a container for bulk fermentation and cover.

Step 3

(1:30 p.m. to 3:30 pm)At warm room temperature, 74-76°F (23-24°C), the warm bulk fermentation should take 2 hours. Give the dough two sets of stretch and folds where the first set is 30 minutes after the beginning of bulk fermentation and the second set is 30 minutes after the first. After the second set, let the dough rest, covered.

Step 4

(3:30 p.m. to 8:00 a.m. the next day)Place the covered bulk fermentation bowl into the refrigerator overnight.

Step 5

(8:00 a.m.)Choose a filling and make it: stir the ingredients in a medium bowl and cover. Remove the dough from the fridge and roll to a 10 x 12-inch rectangle with the short edge closest to your body. Spread the filling over the dough, leaving about 1″ clean on the short side farthest from you. Roll the dough into a tight cylinder. Place the rolled-up log on a baking sheet and freeze for 15 minutes. Fold and place a piece of parchment inside your baking pan to make two “handles.” After 15-minutes, take the sheet pan out of the freezer and using a sharp knife, cut the log in half lengthwise. Pinch the top of the two halves together and braid the dough one strand over the other. At the bottom, pinch the two bottoms together again. Pick up the braid and place it on the parchment right in the middle, then pick up the sides of the parchment and lift the dough and drop it into the pan. Place the pan in a bag and seal.

Step 6

(8:30 a.m. to 12:00 p.m., or until ready)Let the dough rise at a warm temperate, 78°F (26°C), for 3 1/2 to 4 hours, or more. The dough should rise to within 1/2-inch below the rim of the pan.

Step 7

(12:00 p.m.)Preheat the oven with the rack in the middle to 350°F (176°C), non-convection. Line a half baking sheet with parchment paper. In a small bowl, whisk together the egg wash ingredients. Brush a thin layer of the egg wash on the top of the dough. Then, slide the babka on the baking sheet into the oven, bake for 40-45 minutes until the center of the babka reaches 200°F (93°C). While the babka is baking, make the simple syrup by combining the ingredients in a small saucepan, heat until the mixture bubbles a bit, and occasionally stir until the sugar fully dissolves in the water. Cool the mixture. When baked, remove the babka to a cooling rack. Using a plastic spatula, free the short sides of the babka (the sides without parchment) from the sides and bottom of the pan by pressing the spatula down from top to bottom. Brush on a thin layer of the simple syrup and let rest for 10 minutes in the pan. After resting, remove the babka from the pan using the parchment paper “handles” and let cool on a wire rack.