Brioche Dough

1. In a medium bowl, heat the milk to around 110ºF-115ºF. To this, add in the yeast and granulated sugar. If using active dry yeast, let the mixture rest for around 10-15 minutes until the mixture is foamy & bubbly. If using instant yeast, continue to the next step.
2. Add in the eggs, one at a time into the mixture and beat until completely incorporated.
3. In a separate bowl, whisk together the flour and salt. If using a stand mixer, do this in the bowl of the mixer fitted with the dough hook.
4.  Pour the wet ingredients into the dry ingredients and knead the dough until it forms a ball around the dough hook. If kneading using hands, continue kneading until the dough comes together and is no more sticky.
5. Start by adding in one piece of butter at a time, allowing it to fully incorporate before adding the next. Repeat until all the butter is incorporated.
6. Once all the butter is added, you will need to knead the brioche dough until it passes the windowpane test. This shall take around 20-30 minutes by hand depending on the amount of pressure you apply & around 10-15 minutes if using a mixer.
7. To check if the dough is ready, take a decent size piece of the dough and gently spread it out until you can see the light through it. However if the dough tears during this process, it is not ready. Mix for another minute and check again until it passes the test.
8. Once the dough is ready, transfer it to a lightly greased bowl. Cover the dough with a plastic wrap and allow to proof in a warm environment for one hour or until doubled in size. Alternatively, you can proof the dough overnight.

Chocolate Espresso Filling

1. While the dough is proofing, in a microwave safe bowl, add the chocolate (preferably chopped) and cubed unsalted butter.
2. Microwave the mixture in 30 second intervals whisking vigorously in between. Repeat until the chocolate and butter are completely melted. You can also use a double boiler or follow the ‘bain-marie’ method for doing this.
3. Once completely melted, add in the espresso powder and powdered sugar. Mix until completely incorporated.

Assembly

1. On a lightly floured surface, using a rolling pin roll the dough out by applying pressure evenly into a rectangle about 12″ x 18″.
2. Using an offset spatula, spread the chocolate espresso filling evenly all over the dough, leaving a border around the edge. Roll the dough up from the long side. You can also freeze the dough for about 15 minutes at this point to help the filling firm up a bit thus making it easier to shape.
3. Cut the dough straight down the middle, leaving you with two log shaped dough pieces. Shape the dough like a braid by wrapping one exposed piece over the other & always keeping the opened side facing upwards.
4. Transfer the dough gently to a greased loaf pan lined with parchment paper. Cover the braided babka with a plastic wrap and allow to proof in a warm environment until puffy for about one hour. Alternatively let it chill overnight in the refrigerator.
5. Towards the end of the proof time, preheat the oven to 350ºF (177ºC). Brush the babka with an egg white.
6. Bake for about 30-35 minutes rotating halfway through. Brush the babka with sugar glaze if your desire to get a shiny look. Let it cool completely before slicing.
7. Store babka in an airtight container at room temperature for upto 5 days.