01 - Preheat the oven to 400°F. Line two baking sheets with parchment paper.
02 - In a small bowl, combine granulated sugar, ground cinnamon, and optional sea salt.
03 - Sprinkle half of the cinnamon sugar mixture evenly over the work surface. Place the puff pastry sheet on top, then sprinkle remaining cinnamon sugar evenly over the pastry.
04 - Gently roll the pastry with a rolling pin into a 10 by 12 inch rectangle, pressing the cinnamon sugar into the dough.
05 - Starting from one long edge, tightly roll the pastry toward the center. Repeat on the opposite edge until the two rolls meet in the middle, creating a double spiral.
06 - Using a sharp knife, slice the roll crosswise into 1/2 inch pieces to yield approximately 24 slices.
07 - Place the slices cut side up on the prepared baking sheets spaced well apart. Lightly sprinkle with extra granulated sugar.
08 - Bake for 8 to 10 minutes, then carefully flip each palmier and continue baking for another 7 to 8 minutes until golden brown and caramelized.
09 - Allow the palmiers to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool fully.