Step 1

Make the dough: Add the flour, yeast, sugar, and salt to the bowl of a stand mixer fitted with the dough hook attachment and mix on low speed. With the mixer running, add the water, vanilla, egg, and vegetable oil. Increase the mixer speed to medium and continue mixing until the dough is smooth and pulls away cleanly from the sides of the bowl, 7–10 minutes. If the dough is too dry, add more water, about 1 tablespoon at a time, if necessary. If it is too wet, add more flour, 1 tablespoon at a time.

Step 2

Transfer the dough to a clean surface and knead by hand until the dough is completely smooth, elastic, and shiny, 2–3 minutes. Shape into a ball. Grease a large bowl with vegetable oil spray, then transfer the dough to the bowl, cover with plastic wrap, and let rise in a warm place for 45–60 minutes, until doubled in size.

Step 3

Make the filling: Preheat the oven to 300°F (150°C). Line a small baking sheet with parchment paper.

Step 4

Spread the hazelnuts in an even layer on the prepared baking sheet. Roast for about 8 minutes, until golden brown and fragrant. Let cool for 5 minutes then transfer the hazelnuts to a food processor and process until finely chopped, but still with some texture.

Step 5

Melt the butter in a medium saucepan over medium heat. Add the dark chocolate and cook, whisking frequently, until melted and evenly combined. Whisk in the cocoa powder and powdered sugar until completely smooth. The ganache should be spreadable.

Step 6

Make the syrup: Use a paring knife to remove the peel from the orange, then thinly slice the peel.

Step 7

Bring the water to a boil in a medium saucepan over medium-high heat. Add the sugar and stir until dissolved, about 3 minutes. Add the cinnamon and star anise and continue cooking for about 1 minute, then add the orange peel and stir to combine. Reduce the heat to low and cook for 20–25 minutes, until the syrup thickens and the orange peel is tender. Remove the pot from the heat and cover to keep warm.

Step 8

Assemble the babka: Punch down the dough, then transfer to a clean surface and slice in half. On a lightly floured surface, roll out one portion of dough into a 21 x 15-inch (53 x 30-cm) rectangle.

Step 9

Using a silicone spatula, spread half of the chocolate ganache evenly over the dough, all the way to the edges. Sprinkle half of the ground hazelnuts on top. Starting from a long end, roll the dough up into a tight log. Repeat with the remaining dough, then let the logs rest for 15 minutes.

Step 10

Preheat the oven to 365°F (185°C). Line 2 9-inch round cake pans with parchment paper.

Step 11

Using a serrated knife, slice a log in half lengthwise. Cross one side of the log over the other in an X shape with the cut sides facing up. Starting from the center, braid the two halves together to the bottom and top. You can leave as is, or bring the ends together to form a wreath. Transfer to a prepared pan. Repeat with the remaining babka.

Step 12

Make the egg wash: In a small bowl, whisk together the egg and water until smooth.

Step 13

Brush the egg wash lightly over the babka wreaths.

Step 14

Bake the babkas for 25–30 minutes, until golden brown.

Step 15

Meanwhile, heat the syrup to low heat until hot.

Step 16

Remove the babkas from the oven and slowly ladle the hot syrup on top, letting it soak into the babkas. Garnish with dried rose petals and pistachios, if desired.

Step 17

Transfer the babkas to a wire rack and let cool for about 30 minutes.

Step 18

To serve, gently slice the babkas with a serrated bread knife.

Step 19

Enjoy!