Preheat the oven to 400°F, and lightly grease a 9x9-inch baking dish.
Whisk the granulated sugar and brown sugar and cinnamon together in a small bowl. Set aside.
½ cup granulated sugar, ½ cup light brown sugar, 2 teaspoons ground cinnamon
Lightly flour a countertop and use a rolling pin to roll out the puff pastry to a 12x16-inch rectangle.
13 ½ ounces puff pastry dough
Carefully spread the butter over the puff pastry then sprinkle with the sugar mixture leaving an edge exposed at the top. Press the sugar gently into the puff pastry using the back of a spoon.
½ cup salted butter
Starting at the shorter end, tightly roll the dough up into a log. Slice the roll in half then slice each half into 3 pieces and bake for 20-25 minutes or until the tops are golden brown.
To Make the Glaze:
In the meantime, whisk the powdered sugar, milk and vanilla together in a small bowl.