This recipe is a combination of two: Holly's Challah with the addition of vanilla and orange zest to the dough and the chocolate filling from the Chocolate Krantz Cakes in Jerusalem via Smitten Kitchen. A few notes: If you want more guidance making the dough, check out the Holly's Challah post first. Re: hot water*, you can use hot tap water, but if you are worried your tap water is too hot — mine is scalding — you can use ¼ cup boiling water and ¾ cup cold water, which will give you lukewarm water, which will work just fine. This babka can be prepared ahead and baked later. I have had success stopping after I've rolled the dough into coils, but I imagine you could make the recipe up until the point where you place the shaped loaves into the loaf pans. If you do this, cover pans with plastic wrap and place in fridge. The following morning, bring to room temperature before baking — make sure dough feels soft to the touch and is filling the pan before baking. Then proceed with recipe.