01 - In a large bowl, combine warm milk and sugar. Sprinkle yeast over the surface and allow to bloom for 5–10 minutes until frothy.
02 - Incorporate the melted butter, egg, and salt into the yeast mixture. Whisk briefly to combine.
03 - Gradually introduce the flour, mixing until a pliable dough forms. Transfer to a lightly floured surface and knead for 10–12 minutes until the dough is smooth and elastic.
04 - Shape the dough into a ball and place it in a lightly greased bowl. Cover and let rise in a warm environment for approximately 1 hour, or until doubled in volume.
05 - Melt the chocolate and butter together using a double boiler or microwave in short intervals. Stir until smooth, then blend in the brown sugar, cinnamon, and cocoa powder. Set aside to cool to room temperature.
06 - Gently deflate the risen dough. Roll it out on a lightly floured surface to form a 9x14-inch rectangle. Evenly spread the cooled chocolate cinnamon filling over the dough, leaving a ½-inch border along the edges.
07 - Starting from one of the shorter sides, tightly roll the dough into a cylindrical log. Pinch the seam firmly to seal.
08 - Place the rolled log, seam-side down, into a greased 9x5-inch loaf pan. Cover and allow to rise in a warm place for 30–40 minutes, or until noticeably puffy.
09 - Preheat your oven to 350°F (175°C). In a small bowl, combine the topping sugar and cinnamon.
10 - If desired, brush the surface of the risen loaf with melted butter. Evenly sprinkle the cinnamon-sugar mixture over the top.
11 - Bake for 35–40 minutes, or until the loaf is golden brown and sounds hollow when gently tapped.
12 - Allow the loaf to cool in the pan for 10 minutes before carefully inverting it onto a wire rack to cool completely before slicing.