The dough is enriched with butter and eggs, making it a gorgeous, indulgent treat. Loosely rolling the dough will give it room to expand during the second rise. Roll too tight and the dough may split during baking.
To prepare the dough, combine first 3 ingredients in a large bowl, and let stand for 5 minutes or until bubbles form on the surface. Add butter, vanilla, salt, and eggs; stir. Weigh or lightly spoon 5 ounces flour (about 5 cups) into dry measuring cups; level with a knife. Add flour to egg mixture; stir until combined. Turn dough out onto a lightly floured surface. Knead 4 minutes; add enough of remaining 1/4 cup flour to prevent the dough from sticking. Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place, free from drafts, 1 1/2 hours or until doubled in size.
To prepare the filling, combine 1/3 cup sugar and cocoa in a small bowl, stirring well. Combine egg white and 2 teaspoons milk in a small bowl.
Divide dough into two equal portions. Working with one portion at a time (cover remaining dough to prevent drying), roll dough into a 12 x 9-inch rectangle. Melt 1/4 cup butter; brush 1 tablespoon over dough. Sprinkle evenly with half of cocoa mixture, leaving a 1/4-inch border. Sprinkle dough evenly with 2 ounces chopped chocolate. Drizzle with an additional 1 tablespoon butter. Brush far edge with milk mixture. Loosely roll up, starting with a long edge; pinch seam to seal, and tuck ends under. Place dough, seam side down, on a baking sheet lined with parchment paper. Repeat procedure with remaining dough, butter, cocoa mixture, chocolate, and egg white mixture. Reserve remaining milk mixture. Cover dough. Let rise in a warm place 1 hour or until doubled in size.
Preheat oven to 325°.
Brush the dough with remaining milk mixture. Sprinkle each loaf with 2 1/4 teaspoons turbinado sugar. Bake at 325° for 40 minutes or until browned. Cool loaves completely on a wire rack. Cut each loaf into 12 slices.
good but a little intense. Used Mexican chocolate. Might go with lower % for next time. Baking time worked exactly for me.