Chocolate Walnut Babka

To make the dough, in the bowl of an electric mixer, whisk together the warm water, the 1 1/2 tsp. sugar and the yeast. Let stand until foamy, about 5 minutes. Add the 1/4 cup (1 3/4 oz./50 g) sugar, the melted butter, kosher salt, whole eggs and egg yolk and flour. Fit the mixer with the paddle attachment and beat on low speed just until combined, about 30 seconds. Switch to the dough hook and beat on medium speed for 5 minutes. The dough will be wet and elastic but will firm up in the refrigerator.

Remove the dough hook and use a rubber spatula to bring the dough together in the middle of the bowl. Cover with plastic wrap and let stand in a warm spot until doubled in size, about 2 hours, then refrigerate for at least 3 hours or up to overnight.

Meanwhile, make the filling: Put the chocolate in a heatproof bowl. In a saucepan over medium heat, combine the cream, sugar and kosher salt. Bring to a simmer, stirring frequently until the sugar is dissolved, about 5 minutes, then whisk in the vanilla. Pour the cream mixture over the chocolate and let stand for 3 minutes, then whisk until the mixture is smooth and cohesive. Cover and let cool completely. The filling can be made up to 3 days in advance and stored in an airtight container in the refrigerator. Bring to room temperature before using.

When ready to bake the babka, coat a 2 1/2-quart (2.5-l) round French oven with nonstick baking spray.

Lightly dust a work surface with flour, then turn the dough out onto the surface and dust the top of the dough with flour. Knead until the dough is no longer sticky, about 30 seconds, dusting lightly with flour as needed. Cut the dough in half.

Keep one dough half covered loosely with a kitchen towel. Roll out the other dough half into a 10-inch (25-cm) square, dusting the surface with flour as needed to prevent sticking. Using an offset spatula, spread half of the filling over the dough, leaving a 1/2-inch (12-mm) border uncovered all around. Sprinkle with half of the walnuts.

Starting with the side closest to you, roll the dough tightly into a log. Turn it vertically, seam side down, so one end is facing you. Starting 1 inch (2.5 cm) from the top, use a sharp serrated knife to cut the log in half lengthwise. Carefully turn the cut sides facing up and twist the strands together, tucking the gathered ends under the twist. Transfer the twisted dough to the prepared pan, positioning it over to one side.

Repeat with the remaining dough half, then transfer it to the pan, positioning it on the opposite side and overlapping the two portions slightly toward the center. You want them to bake into one another, so arrange as such.

Cover the pan loosely with plastic wrap and let stand in a warm spot until puffed up slightly, about 1 1/2 hours.

Near the end of the rising time, position a rack in the lower third of an oven and preheat to 350°F (180°C).

Bake the babka until the top is deep golden and an instant-read thermometer inserted into the center registers 185°F (85°C), 35 to 45 minutes. If the babka is getting too dark on the top, cover loosely with aluminum foil.

Meanwhile, make the syrup: In a small saucepan over high heat, whisk together the sugar and water until the sugar dissolves and the mixture comes to a slight boil, about 2 minutes. Remove from the heat.

Transfer the pan with the babka to a wire rack and let cool for 15 minutes, then invert it out onto the rack. Brush the top and sides with some of the syrup, then let stand for 5 minutes and brush again. Sprinkle with flaky sea salt. Let cool for 10 minutes more. Cut the babka into slices and serve warm or let cool completely. The babka is best enjoyed the day it is baked. Serves 8 to 12.

Williams Sonoma Test Kitchen