Ingredients
for the dough:
3/4 cup|170 grams whole milk
30 grams fresh yeast
2 1/4 cups|325 grams bread flour, sifted
2 1/4 cups|325 grams pastry flour, sifted
2 large eggs, at room temperature
1/2 cup|110 grams granulated sugar
1/2 teaspoon vanilla extract
1/4 teaspoon kosher salt
8 1/2 tablespoons|120 grams unsalted butter, at room temperature, cut into cubes
for the chocolate filling:
450 grams Nutella
1 1/3 cups|200 grams bittersweet chocolate chips
1. Pour the milk into the bowl of a stand mixer fitted with the dough hook. Break up the yeast into the milk and dissolve it into the milk with a whisk or using your fingertips. Dump the flour on top of the milk, then the eggs on top of the flour, then the sugar, then the vanilla, then the salt, then half of the butter. Begin mixing at the lowest speed. After 2 minutes increase the speed to medium and continue mixing for another 5 minutes, scraping down the bowl, if necessary, so that it all mixes together. The dough should begin to come together but won’t be smooth.
2. Reduce the mixer speed to low and slowly add the rest of the butter, cube by cube, only adding more butter once the previous cube disappears into the dough. This process should take 2 to 3 minutes. Once all of the butter is incorporated, turn off the mixer. The dough should be smooth and elastic.
3. Lightly flour a work surface with bread flour, and turn the dough out onto the floured surface. Knead the dough into a smooth ball.
4. Form the dough into a rectangle (measuring about 10 inches by 6 inches) and place on a tray. Cover with plastic wrap and refrigerate for at least 2 hours but up to 12 hours.
5. Lightly grease four 8 1/2-inch-by-4 1/2-inch loaf pans with nonstick baking spray. Lightly flour a work surface with bread flour, and transfer the dough to the floured surface. Lightly flour a rolling pin and roll the dough into a rectangle measuring about 36 inches by 9 inches—it’s fine if the rectangle is bigger (up to 40 inches by 12 inches) but no smaller than 36 inches by 9 inches. If the dough shrinks back as you roll it out, cover it with a towel or plastic wrap for 5 minutes to let it rest and then continue rolling again.