Sprinkle a cool, flat surface with Granulated Sugar (1 cup). Gently open up the sheet of Puff Pastry (2 sheet) and lay flat on top of the layer of sugar. Sprinkle sugar evenly all over the sheet of puff pastry.
Fold the long sides of the pastry in ¼ of the way, then sprinkle with more sugar.
Fold the long sides toward each other again so they meet in the middle, and sprinkle with more sugar.
Using a rolling pin, gently roll down the sheet of puff pastry to deepen the creases so the rectangle will hold the shape. You don’t want it unfolding again!
Fold the rectangle in half one more time, and gently roll down the strip of dough so that it is pressed together and holds its shape. Again, you do not want to make the dough thinner, you are just ensuring it stays folded. Place in the fridge for 30 minutes to chill on a parchment-lined baking sheet.
Preheat the oven to 400 degrees F (200 degrees C) and line a baking sheet with parchment paper.
Remove the dough from the fridge and slice into ¼-inch pieces. Place the slices on a parchment-lined baking sheet cut-side down, so you can see all the little folds in the dough. Make sure the folds stay tightly together. Allow plenty of space between each one, as the dough will expand on both sides as they bake.
Place them in the oven and begin checking them after about 5 minutes. Cook time could be anywhere between 5–15 minutes depending on how big your palmiers are.
Once the palmiers are caramelized on the bottom, carefully flip each one over with an offset spatula and return to the oven for 5 more minutes.
Remove palmiers from the oven and allow them to cool on a wire rack. Again, transfer them with an offset spatula and take care not to burn your fingers.