Preheat the oven to 425 degrees F. Line a large sheet pan with parchment paper and set aside.
Combine the sugar and salt. Pour 1/4th of that mixture on a flat surface and unfold one sheet of THAWED puff pastry onto the sugar. Add another 1/4th of the sugar mixture on top spread it evenly.
Using a rolling pin, roll the dough until it's 13 by 13 inches and the sugar is really pressed into the puff pastry on top and bottom.
Fold the sides of the square towards the center so they go halfway to the middle. Fold them again so the two folds meet exactly at the middle of the dough. Then fold those two halves together.
Slice that log of dough into 3/8-inch slices and place the slices on the prepared baking sheet. Sprinkle leftover sugar mixture on top of the sliced cookies.
Repeat with the other puff pastry.
Bake the cookies for 6-8 minutes or until caramelized and brown on the bottom, and then flip over with a spatula and bake another 5-7 minutes, until caramelized on the other side.
Transfer to a baking rack to cool.