Punch down the dough, and transfer it to a lightly floured work surface. Roll into an 18 x 10-inch rectangle (dough should be an even thickness; about ¼-inch thick). If the dough keeps contracting while rolling, cover with plastic wrap and allow the gluten in the dough time to relax (see Chef’s Tips).
The long edge (18-inch) of the rolled-out dough should be parallel to the edge of your work surface. Spread the butter onto the rolled-out dough, leaving about ½ inch free of butter at the furthest end.
Evenly sprinkle the cinnamon sugar over the surface of the butter. Gently rub and pat the sugar mixture into the butter, being careful not to tear or stretch the dough. After sprinkling the surface with cinnamon sugar, lightly brush the free edge with some water before rolling dough into a tight log. Pinch the seam together when you reach the dampened edge (see Chef’s Tips for how to make into heart-shaped rolls).
With the seam side down, slice the log using a length of unflavoured dental floss (or thread). Slide the floss under the roll 2 inches from one of the ends, cross the two ends at the top of the roll and pull tightly in opposite directions until the floss cuts through the roll. Repeat the process at 2-inch intervals until the entire roll is cut.
Arrange the 9 rolls in the prepared baking pan, spaced evenly apart. Cover with plastic wrap or a damp kitchen towel. Place in a warm, draft-free location to proof until almost doubled in size; about 30 to 35 minutes. To check if the rolls are ready for baking, perform the poke test (see Chef’s Tips).
Halfway into the proofing time, preheat oven to 350°F (177°C).
Place cinnamon rolls into the preheated oven; 25 to 30 minutes. Rotate pan halfway through the baking time. Continue baking until a thermometer reads just below 190°F (88°C) at the centre of the pan. Do not overbake, or the rolls will be dry.
While the rolls are baking, make the icing.