Roll dough into a 20x18 inch (50x45cm) rectangle. Spread the butter all over it, leaving a 1-inch (2,5cm) border at the long side where you end up rolling. Sprinkle sugar mixture and chocolate on top of the butter evenly. Roll-up long side tightly, cut into 12 equal-sized pieces and transfer to the prepared baking sheet. Don't cover rolls. Turn off preheated oven and place rolls in the oven to rise for about 30 minutes, until doubled in size. Leave the wicket ajar.