For the uninitiated, a Babka is a kind of swirled coffee cake - a sweet yeast dough is rolled out very thin, sprinkled with filling, rolled up and twisted, sprinkled with streusel and baked. The filling for this babka was submitted by someone named Lilia on allrecipes.com - it is the best chocolate babka filling in my experience. I use my favorite challah recipe - Andrea's Challah - for the dough. Feel free to use the yeast dough of your choosing. For brevity's sake, I'm starting this recipe with the assumption that the dough has already been made and risen once, and there is enough for 2 Babkas (about 1/4 of the Andrea's Challah recipe).