With the addition of buttermilk, this babka takes on a wonderfully tart flavor that complements the sweet swirls of chocolate hazelnut butter. Great with a little bit of butter. The leftovers also make great french toast or bread pudding!
Heat your buttermilk to 110°F and stir in 1 tablespoon sugar. Once dissolved, add yeast. Let activate for ten minutes.
While activating, combine flour and sugar in stand mixer. Add in yeast mixture. Begin to stir with the dough hook on Level 1. When the yeast mixture is almost fully incorporated, add an egg one at a time. Then, add in small chunks of butter. When mixture is homogenous, turn mixture to 3 and let knead for 5 minutes. Dough should be sticky, but you should be able to pull away a piece and have it pass the window pane test. If not, let it mix for another minute and test again.
Transfer dough to a greased bowl. Cover in cling wrap and drape with a towel in a warm place until doubled in size (2 hours on a warm day, 3-4+ on a cold).
Braiding and Second Rise
Once doubled, turn out on a floured surface. Roll into large rectangle with the dough about ⅛" thick.
Spread chocolate hazelnut spread in a thin layer to the edge of the dough. Tightly roll the dough along the longest side (so you're left with a very long log). Divide into half. With your first half, cut the dough down the center of the spiral (you'll now see the swirl exposed). Twist the two halves, with the exposed lines of the spread to the top of the twist. Repeat with second half. Place in greased bread pans, cover, and place in fridge for 8-20 hours.
When ready to bake, remove dough and place on top of stove to come to room temperature.
Preheat oven to 350°F.
Take one egg and beat into froth, brush onto dough. Bake bread for one hour, until top is a deep, golden brown. Let cool and enjoy!