Make the Dough:

1. Zest 2-3 small oranges, set aside 1 tsp. for the dough and let the remaining zest dry until ready to use in the filling. Allowing the zest to dry makes it easier to incorporate evenly throughout the filling.
2. In the bowl of a stand mixer, add the white whole wheat pastry flour, all-purpose flour, granulated sugar, 35 grams cocoa powder and kosher salt. Whisk or stir to combine.
3. In a saucepan, add the milk, and 4 Tbsp. butter. Heat until the butter is melted and an instant-read thermometer registers 120 degrees F – 130 degrees F.
4. Pour the warm milk mixture over the flour mixture. Using the paddle attachment, beat the mixture at low speed until combined, and there are no remaining bits of dried flour, about 2-3 minutes.
5. Add sourdough starter and mix thoroughly. Cover and let rest for 15 minutes.
6. Add the eggs, one at a time, the vanilla extract, and 1 tsp. orange zest. Beat until a shaggy dough forms. Scrape down the sides of the bowl as necessary.
7. Switch to the dough hook and beat at medium-low speed until the dough is smooth, and elastic and begins to pull away from the sides of the bowl. If the dough is too sticky, add in additional all-purpose flour, 1 tablespoon at a time, until the desired consistency is achieved.
8. Cover and let the dough rest in the mixer bowl for 30 minutes.
9. Remove the dough to a large clean bowl. Stretch and fold the dough over itself a few times in the bowl. Form it into a ball and place it back in the bowl.
10. Cover and allow the dough to rise at warm room temperature for 3-4 hours, until the dough leaves a slight indentation when lightly pressed with a wet finger. Perform two additional folds after the 1st and 2nd hour.

Optional Cold Ferment:

1. Instead of the 3-4 hour bulk ferment on the counter at room temperature, allow the dough to cold ferment overnight in the refrigerator.
2. After mixing the dough, cover and let the dough bulk ferment for 1 hour. Gently press down the dough to degas it. Fold the dough by gently folding the edges into the center.
3. Cover, and let the dough rest for an additional 1 – 1 1/2 hours, until doubled in size. Pat the dough into a small rectangle, cover it with plastic wrap, and place it in the refrigerator for 8 to 24 hours. The overnight rest in the refrigerator allows the dough to stiffen up for shaping.
4. Remove the dough from the refrigerator and allow it to warm up to room temperature for 30 minutes or so before rolling out.

Make the Filling:

1. In the meantime, mix 76 grams melted butter, 156 grams brown sugar, 14 grams cocoa powder, 6 grams cinnamon, and 12 grams orange zest in a small bowl.

Shape / Final Rise / Bake:

1. Line a 9×5 inch loaf pan with parchment paper. Grease any exposed areas with butter.
2. Turn the dough out onto a lightly floured surface. Roll into a 12×18-inch rectangle with one long side facing you. Roll it out as evenly as possible.
3. Carefully spread the filling over the dough, leaving a border around the edges.
4. Starting from the long end nearest you, roll the dough up tightly into a log. Pinch the seam to seal.
5. Using a sharp knife or bench knife, slice the dough into six 3-inch pieces. Place the rolls in the prepared loaf pan. Cover and let the rolls rise at warm room temperature until puffed, 1-2 hours, or until the dough leaves a slight indentation when lightly pressed with a wet finger.
6. Preheat the oven to 350 degrees F. and place a rack in the middle.
7. Place the loaf pan on a rimmed baking sheet. Bake the sweet roll bread for 30-35 minutes, until the centers of the rolls are set, and an instant-read thermometer inserted in the center registers 190 degrees F. Let cool in the pan for 10 minutes. Then top with the sugar/orange glaze.

Powdered Sugar/Orange Glaze:

1. In a small bowl, whisk together confectioners’ sugar and orange juice. Drizzle over the top of the rolls using the tines of a fork or a wire whisk.