To make the tangzhong: In a medium saucepan set over medium heat, bring the water, butter, sugar, and salt to a boil.  , When the butter is fully melted, add the flour all at once then stir to combine. The mixture will quickly form a ball that follows the spoon or spatula around the pan; this will take just 20 to 30 seconds. , Remove the pan from the heat and transfer the mixture to a large bowl or the bowl of your stand mixer fitted with the flat beater attachment; spread it across the bottom of the bowl to help it cool. Let it rest for about 5 minutes uncovered. , To make the dough: With the mixer running, add the eggs to the lukewarm tangzhong one at a time, making sure the first egg is fully incorporated before adding the second. Beat until the mixture is shiny and quite smooth.  , Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Add the flour, water, yeast, and vanilla to the bowl, mixing to form a soft, sticky dough. , Change to the dough hook and knead for 5 to 7 minutes, until springy. If you’re using a mixer it probably won’t clean the sides of the bowl; that’s OK. Cover the dough and let it rise until it’s nearly doubled in size, about 1 1/2 hours. , To make the filling: In a small bowl, mix all of the ingredients together until smooth. If the cream cheese isn’t soft enough to work with easily, microwave the mixture very briefly, then stir to combine; set aside. , To make the streusel: In a medium bowl, use your fingers to combine all of the ingredients until the mixture is sandy and crumbs form; some larger, pea-sized pieces are OK. Set it aside.   , To fill and shape the babka: Gently deflate the dough in the bowl, then transfer the dough to a lightly greased surface and roll it into a 9" x 18" rectangle, letting it rest for 5 to 10 minutes if it resists stretching. , Spread the filling over the surface of the dough, leaving a 1" border bare on all the edges. Starting with a short end, roll the filled dough into a cylinder, sealing the seam and ends as best you can. , Lightly grease a 9" x 5" loaf pan. Or grease the pan and line it with a loaf pan lifter.  , Using a bench knife or a sharp knife, cut the log in half lengthwise to make two pieces of dough each about 10" long.  , With the exposed filling side up, wrap the two pieces around each other to form a short twist, tucking the ends underneath. Carefully transfer the loaf to the prepared pan. Sprinkle the prepared streusel evenly over the top. , Let the babka rise, covered, for about 1 1/2 hours, until it’s barely crested over the rim of the pan. Near the end of the rising time, preheat the oven to 350°F. , To bake the babka: Bake the babka for 30 minutes. Lightly cover the top with aluminum foil, and bake for an additional 25 to 30 minutes, until it’s golden brown and the interior measures about 195°F with a digital thermometer. , Remove the babka from the oven, and immediately loosen the edges with a heatproof spatula or table knife. Let the babka cool for 10 minutes, then lift it out of the pan onto a rack to cool completely before slicing. , Storage information: Store the completely cooled babka, well wrapped, at room temperature for several days, or refrigerate it for up to a week. Reheat slices stored in the refrigerator before enjoying.