Sprinkle around half of the remaining sugar evenly onto a large cutting board or marble work surface in a rectangle the same size as your puff pastry sheet.
Place the puff pastry sheet on top, and sprinkle evenly with the remaining sugar. Use a rolling pin to gently roll out the puff pastry dough to an 11x11-inch square, pressing in the sugar as you roll. Use the sugar to make sure the dough isn’t sticking to the cutting board, and try to make sure it is covering both sides of the dough evenly.
Fold down the top quarter of the dough and fold up the bottom quarter of the dough so that they meet horizontally in the middle. Sprinkle the reserved tablespoon of sugar over any spots that don’t seem well covered with sugar.
Fold the left-hand side of the dough over to meet the right, like you are closing a book. The raw edges should be all stacked on the right-hand side.
Using a round chopstick, press down through the dough layers in a horizontal line directly in the middle, but do not cut through the dough. (By making this indentation, you will be able to fold the dough again and have the edges line up.)
Fold dough in half horizontally using the indentation you have created. Carefully move the folded dough to the refrigerator and chill for 45 minutes.
Preheat oven to 415° Fahrenheit while dough is chilling, for at least 30 minutes.
When dough is firm, place on cutting board and cut into slices about ¼-inch thick. You should get about 12 slices.
Place the slices carefully on a parchment paper-lined baking sheet. They spread out to about three times as wide as they are, so I recommend baking only 6 at a time.
Bake for 10-12 minutes, until sugar begins to caramelize and brown on the bottom. Use a spatula to flip them over, then bake another 4-6 minutes, until they are fully browned.
Remove pan from oven.
After 2 minutes, use a spatula to transfer cookies to a cooling rack to cool completely.
If you’d like to dip them partly in chocolate, melt dark chocolate melts in a candy melter, double boiler, or microwave (stir every 30 seconds).
Then dip half of the palmiers into the chocolate and set on a sheet of wax paper to cool and harden.
Notes
Storage Tips: Cookies will last for several days in an airtight container at room temperature.Expert Tips: Try to get as much sugar as you can pressed into the dough when rolling it out. It helps the cookies keep their shape and also gives you more caramelization. Oven temperature is critical for this recipe. Your oven needs to be preheated for at least 30 minutes before baking, and if you have an oven thermometer, it’s good to check to make sure the oven temperature hasn’t dropped. If your oven is too hot, the sugar will burn before the pastry is cooked. If it is not hot enough, you won’t get that shiny caramelization on the sugar on your palmiers. Watch the timing closely—you want to be able to see that the edges of your palmiers are browning but not totally browned before you flip them. On some ovens this may happen sooner than others. They will continue to cook after you flip them, so you want them to be not quite at the final caramelization level you are looking for. Also, the amount of caramelization is up to you. Wait a little longer to flip them if you like that deep dark, almost bitter caramelization. Or flip them early if you just want them lightly golden brown.Puff pastry is notoriously hard to work with, and becomes too soft if you let it sit out at room temperature. Rolling out on a cold marble surface helps it stay cold. You can also always put it back in the refrigerator if it is getting too warm to work with.If you don't have candy melts, try melting dark chocolate with a little bit of coconut oil.