Line a baking sheet with a silicone mat or parchment paper.
On a lightly floured surface, roll out the dough to form an 18 x 10-inch (48 x 25 cm) rectangle that is 1/4 inch (5 mm) thick. Cut the sides slightly to straighten them out. Cut the dough into 8 equal rectangles measuring 10 x 2.5 inches (25 x 6 cm) each.
Divide the chocolate evenly among the rectangles by making a first line of chocolate 1 inch (2.5 cm) from one of the short edges, and a second line 2 inches (5 cm) from that same edge. Roll the edge of dough up over the first line of chocolate, then keep rolling to make 4 more turns. Place the dough rolls seam side down on the prepared baking sheet, spacing them out evenly. Cover with plastic wrap. Let rise at room temperature for 1 hour or until the dough has doubled in volume.
With the rack in the middle position, preheat the oven to 350°F (180°C).
With a pastry brush, gently brush the dough rolls with the beaten egg, covering them completely.
Bake for 25 minutes or until golden. Let cool on a wire rack.