Remove the dough from the fridge and let it sit out until pliable enough to handle, about 30 to 60 minutes.
Grease two 8 x 4 inch loaf pans, then line the bottom and long sides of each pan with a sheet of parchment paper, leaving a bit of extra paper along the sides. You'll use this later on to remove the babka from the pans.
Once the dough feels pliable enough to work with, cut it in half.
Lightly flour a work surface, then place one of your dough halves on it. Roll the dough into a thin, approximately 12 x 16 inch rectangle.
Spread half of the filling evenly over the dough.
Starting with one of the long sides, roll the dough into a tight snake.
Use a knife to cut the dough snake in half, cutting lengthwise to create two long halves with the filling exposed.
Gently twist the two dough halves around each other. Try to arrange them so that the inner parts with the filling exposed are on top, but don't fuss too much.
Gently transfer your dough twist to one of the prepared loaf pans. You may need to compress it a bit.
Repeat the assembly process using the second dough half and the remaining filling.
Take the streusel out of the fridge. It will feel pretty solid at this point. Use a fork to break it up, then sprinkle the crumbs over your unbaked loaves
Cover the loaves with a damp tea towel and place them in a warm location. Let them rise until they've puffed up just a bit, about 90 minutes. They won't significantly increase in size, but you should see some of the gaps in the pan filled in.
Preheat the oven to 350°F.
Bake the babka until the loaves have puffed up a bit more, any exposed crust is golden brown, and the topping has darkened, about 40 to 45 minutes. The best way to test them for doneness is with an instant read thermometer — the internal temperature should be between 190°F and 195°F.
Place the pans on a cooling rack. Let the loaves cool in the pans for about 20 minutes, until they feel set, then use the parchment paper to gently lift them out of the pans. Let them finish cooling on the racks.
Slice and serve.