Cinnamon Swirl Bread with Prunes

Instructions

1. Make the sponge: In a bowl, whisk together the flour, wheat bran, water, and yeast and let sit at room temperature for 30 minutes. Refrigerate overnight. Bring to room temperature 1 hour before proceeding to the next step.
2. Make the dough: Mix the flour and yeast into the sponge until a shaggy dough forms. In a stand mixer fitted with a paddle attachment, briefly mix the butter. Add the sponge-flour mixture to the butter and mix on low speed until the butter is no longer sticking to the sides of the bowl. Let rest 20 minutes.
3. Attach the dough hook to the mixer. Add the salt and mix on medium speed until butter is thoroughly incorporated and the dough pulls cleanly away from the sides of the bowl, 5 minutes. Add prune bits or dried plums and mix on low speed until evenly distributed.
4. Put the dough in a lightly oiled bowl, cover, and let rise until doubled in volume, about 1 1/2 hours. Place the dough on a lightly floured surface and pat into a rectangle. Fold in 3 folds like a business letter. Return the dough to the bowl, cover, and refrigerate for 1 hour.
5. Make the filling: In a small bowl, combine sugar, cinnamon, dried plum powder, and orange zest.
6. Put the dough on a lightly floured surface and cut it in half. Roll each half into a 7 x14-inch (18 x 35.5-cm) rectangle. Brush surface with egg wash, leaving a 1/2-inch (1.25-cm) border. Sprinkle with half the cinnamon filling. Starting with the short end of the rectangle, roll dough into a log, then gently roll the log to eliminate air pockets. Repeat with the remaining dough and filling.
7. Oil two 8 x 4-in. (20 x 11-cm) loaf pans. Tuck in ends of the each log and place, seam-side down, into the pan. Loosely cover and let rise until dough no longer springs up when lightly pressed, about 1 1/2 hours.
8. Preheat oven to 350F (180C). Bake, rotating once, until the tops and edges are golden brown, about 50 minutes. 
9. Cool in the pans for 5 minutes, then unmold and cool completely.