01 - Preheat oven to 400°F (200°C). Line a baking tray with parchment paper.
02 - Unroll the sheet of puff pastry onto a lightly floured work surface.
03 - In a small mixing bowl, blend brown sugar, cinnamon, salt, and vanilla extract if using.
04 - Brush the surface of the pastry evenly with melted butter.
05 - Evenly scatter the cinnamon-sugar mixture over the buttered pastry.
06 - Starting from a long edge, roll the pastry tightly into a log. Slice into 12 equal rounds using a sharp knife.
07 - Place the swirls cut-side up onto the prepared tray, leaving room for expansion.
08 - Bake for 16 to 18 minutes until golden brown and puffed.
09 - Transfer baked swirls to a wire rack and cool completely.
10 - Whisk powdered sugar with 1 to 2 tablespoons of milk until smooth. Drizzle the glaze over cooled swirls.