- 5 cups all-purpose flour
- ½ cup sugar
- 1 packet (¼ oz.) instant or fast-rising yeast
- 1 tsp. fine sea salt
- 1 cup milk heated to 120 degrees
- 3 eggs at room temperature
- 1 tsp. vanilla extract
- 10 Tbsp. unsalted butter, softened
- 8 Tbsp. (1 stick) unsalted butter
- 4 oz. bittersweet or semisweet chocolate (at least 60% cocoa solids)
- ¾ cup powdered sugar
- ⅓ cup cocoa powder
- ⅓ cup water
- ¾ cup sugar
- ½ to 1 tsp. optional flavoring (orange blossom water, rose water, vanilla extract, or fruit-flavored liqueur)
- Place the flour, sugar, yeast, and salt in the bowl of a stand mixer fitted with the paddle attachment. Add the warm milk and mix until a shaggy dough forms.
- Add the eggs one at a time, followed by the vanilla extract, scraping down the sides as necessary. With the motor running, add the butter one tablespoon at a time until it is fully incorporated. (This may take a few minutes. Be patient.)
- Switch to the dough hook and knead, periodically scraping down the sides and turning up the dough at the bottom of the bowl. Continue kneading until the dough is smooth and shiny, about 10 minutes. (You can also knead the dough by hand at this point.)
- Place the dough in a well-oiled bowl, cover, and let rise in a warm place until it is puffy and has expanded by 50%, 1 hour to 90 minutes. If time permits, a slow rise in the refrigerator is preferable: place the covered bowl with the dough in the refrigerator and allow it to rise for at least six hours, or overnight up to 24 hours. (This method will result in better flavor and a more manageable dough.)
- When the dough has risen and you are ready to fill and shape the babka, grease and flour two 9×5 loaf pans. To prepare the chocolate filling, combine the butter and chocolate in a small saucepan and place them over low heat until both have melted. Remove from heat and set aside.
- Sift the powdered sugar and cocoa powder together into a small bowl. Add the melted butter and chocolate mixture and stir until you have a smooth paste. Set aside while you roll out the dough.
- Divide the risen dough in half. Wrap the half that you are not using in plastic and refrigerate it until needed. Place the first dough half on a lightly floured board and roll out to a rectangle of approximately 15×11 inches. Place half of the chocolate filling on top of the dough and use an offset spatula to spread a thin layer of the filling all the way to the edges.
- Starting with the long end, roll the dough into a tight jellyroll and pinch the ends closed. Trim off a small piece from either end and discard. Using a serrated knife, cut the roll down the middle lengthwise to expose the filling. Turn the two halves on their backs so that the cut side is facing up. Pinch the two ends together and lift the right half over the left half. Then lift the left half over the right half. Repeat until the entire loaf is twisted. Carefully transfer the twisted dough to the greased loaf pan. Repeat the process with the second half of the dough and the remaining chocolate filling.
- Cover the loaves with a clean tea towel and allow to rise in a warm place until increased in size by 10 to 20%, 40 minutes to one hour. Preheat the oven to 350°F.
- Once the loaves have risen for the second time, bake them in the oven for 50 to 60 minutes until a skewer inserted in the middle comes out clean. (If the top begins to brown excessively before the inside is fully baked, cover the top with foil.)
- While the loaves are baking, make the syrup. Combine the water, sugar and additional flavoring, if using, in a small saucepan and bring to a boil, stirring to dissolve the sugar. Remove from heat and allow the syrup to cool.
- Once the loaves are baked, remove them to a cooling rack. While the loaves are still warm and in the pans, brush the syrup over the tops and sides. (If syrup begins to pool on top, wait five minutes for it to absorb and then add the remaining syrup.)
- Allow the loaves to cool completely before removing from the pans.
- Serve warm or at room temperature.