Grease two 2¼-lb (9 by 4 inches or standard American size will work just fine) with some oil or just spray with whatever non-stick spray you use. Then cut a piece of parchment to line the pan and make it wide enough to overlap each side and create “handles” so when the babka is done, you can just pull it right out of the pan.
Make the filling by mixing together the confectioners’ sugar, cocoa powder, chocolate, and butter. (Note here: I melted my chocolate and butter together in my microwave on the melt function. The chocolate melted a bit faster but by mixing them vigorously, it all came together and became a lovely shiny ganache like mixture.) You will get a spreadable paste once you add the sugar and cocoa powder to the butter/chocolate mixture.
Divide the dough in half and keep one-half covered in the fridge. Each half should be about 19 ounces each if you are one to measure and not just eyeball.
Roll out the dough on a lightly floured surface into a rectangle measuring 15 by 11 inches. Don’t get crazy here – anything close to this size is fine. Position the dough so that a long side is closest to you. Using an offset spatula if you have one, spread half (about 5/8 cup) of the chocolate mixture over the rectangle, leaving a ¾-inch border all around. Sprinkle half the pecans and the sugar over the chocolate. (if you plan to use cinnamon as well you can sprinkle on now or have it already mixed into the sugar and sprinkle the mixture all over the chocolate.)
Have a little bowl of water handy and use a small pastry brush or your finger to brush a little bit of water along the long end farthest away from you.
Use both hands to roll up the rectangle like a roulade or as I like to think about it, a sushi roll. Start from the long side that is closest to you, start rolling gently but firmly, get the first roll started then check as you go along that you are keeping it tightly rolled along the whole length of dough. Repeat the rolling until you reach the other long end. Press to seal the dampened end onto the roulade and then use both hands to even out the roll into a even cylinder and turn it around so it is resting on its seam.
Trim about ¾ inch off both ends of the cylinder with a serrated knife. Use the serrated knife to gently cut the roll into half lengthwise (yes that’s right – lengthwise), starting at the top and finishing at the seam. This is where you’ll be glad you rolled it tightly but if the layers separate a bit, don’t panic. It’s going to be ok. You’ll end up with two halves revealing all the layers of dough and filling. With these cut sides facing up, press together one end of both halves, and then lift the right half over the left half and repeat this until there is no more dough left. Press together the dough at the finished end. Now you should see a twist with the filling and layers showing on top. Carefully lift the cake and place it into the prepped loaf pan. If it is a bit too long, just snug it in. It will be fine. Cover the pan with a wet dish cloth or tea towel and leave to rise in a warm place for 1 to 1½ hours. The cake will rise by 10 to 20 percent. Repeat the whole process to make the second cake. If you have to leave like I did while the cakes are in the second rise, be sure to put them in the fridge to slow the rise. I left them too long during one of my bakes and they overproofed a bit – almost doubled in size. I think they turned out ok but it threw off the bake a bit and possibly the texture of the bread.