Method
1. In the bowl of a stand mixer, mix the yeast with milk and sugar and flour
2. Let rest until small bubbles appear and break the surface, about 10 to 15 minutes
3. With the mixer fitted with the dough hook, on low speed, mix in the 3 ounces butter then the egg and salt
4. Gradually add the flour until it’s incorporated
5. Turn the mixer to medium-high speed and knead the dough until smooth, about 5 minutes
6. Either cover the bowl with a kitchen towel and refrigerate the dough for 6 hours, or overnight, or roll out in the next step
7. Butter a 9-inch (23cm) loaf pan and line the bottom and up the sides with a piece of parchment paper overhanging the two long sides
8. To make the filling, melt the 3 1/2 ounces of butter in a medium saucepan
9. Add the sugar and stir until dissolved or almost completely dissolved
10. Remove from heat and add the chocolate
11. Let stand 1 minute, then stir until the chocolate is melted and smooth
12. Stir in the cocoa powder and cinnamon. Set aside
13. On a lightly floured surface, roll the dough (chilled or at room temperature) to a rectangle 12 x 20-inches (30 x 50cm)
14. Spread the chocolate filling over the surface of the rectangle all the way to the edges
15. Strew the nuts and cookie or brownie bits (if using) over the chocolate
16. Starting at one of the long ends of the rectangle, roll up the dough tightly so you have a log that’s 20 inches (50cm) long
17. Using a sharp knife, slice the dough completely in half lengthwise
18. With the cut sides facing up, overlap the end of one cut half over the other (with the cut sides still facing up), then take the other cut half and fold it over the other, making sure the cut sides are always facing up
19. Lift the twisted loaf and squish it into the prepared loaf pan by pushing in on the two ends, so it fits in nicely
20. Put the loaf pan in a very warm place, such as near a radiator or in an oven that has a pilot light, and let rise for about two hours, until it’s puffy and almost doubled in size
21. While the dough is rising, make the syrup by bringing the water, sugar, and honey to a boil in a small saucepan
22. Let boil for 4 minutes, skimming off any foam that rises to the surface with a spoon. Remove from heat and set aside
23. Fifteen minutes before you bake the babka, preheat the oven to 375ºF (190ºC)
24. Bake the babka on the middle rack of the oven for 30 minutes, or until a skewer inserted into the center (in a part where there is less chocolate filling), comes out clean of dough
25. Remove the babka from the oven and spoon or brush the room temperature syrup over the babka and let cool completely before lifting the babka out
26. Let cool loaf pan completely, then serve