A homemade babka that's soft and airy, has ripples of Nutella throughout, and leavened using just your sourdough starter! It's good sliced warm, slathered with butter, toasted as leftovers, and also makes some of the best French toast known to man. Makes 1 loaf
Add the water, starter, sugar, and eggs to the bowl of a stand mixer fitted with the dough hook. Mix on low speed until well combined. Add the flour and salt and knead on low speed until the dough comes together - about 3 minutes. Add the butter gradually until dispersed. Cover and rest for 30 minutes.Knead on LOW speed (not past speed 2) for 6-8 minutes. Transfer to a greased bowl, cover, and let rise at room temperature until doubled in size - about 10-12 hours. Turn the dough out onto a lightly floured worksurface. Roll into a roughly 10 by 15-inch rectangle. Spread the Nutella over top, leaving a 1-inch border on all but one of the longer sides. (You may need to heat the Nutella slightly just to make it easier to spread.) Beginning with the long borderless side, roll into a tight log. Pinch the seam to seal.Using a sharp knife or kitchen shears, cut the log in half longways to make two tails of dough, leaving 1-2 inches attached at the top. Turn the tails 90-degrees outward so the strips of dough and filling are facing upward. Twist the tails over each other until you reach the end. Pinch the ends to seal and tuck under the loaf. Transfer to a greased loaf pan, cover loosely with plastic wrap, and let rise at room temperature until the dough rises 1-inch above the rim, about 2 hours. Bake at 375 degrees on a sheet pan lined with parchment paper for 45-50 minutes, until baked through and well browned. Cool in pan 10 minutes before inverting to release. Cool completely on a metal rack before slicing.