Preheat the oven to 450 degrees and line a baking sheet with parchment paper.
Combine 1/2 cup of the sugar and kosher salt and pour it over a flat surface such as a wooden board or marble slab. Unfold the sheet of puff pastry and place it on top of the sugar mixture.
Combine the remaining 1/2 cup of the sugar and cinnamon and sprinkle evenly over the pastry. Lightly roll the dough with a rolling pin pressing the sugar in the pastry until it's a 13 inch square.
Fold the sides of the square toward 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 one half over the other half as though closing a book. Slice the dough into 1/2-inch slices and place them cut up on the prepared sheet.
Bake for 6 minutes, or until caramelized on the bottom, then carefully turn with a spatula and bake for another 3 to 5 minutes, until caramelized on the other side. Transfer to a baking rack to cool. Don't worry if they look funky when you flip them. Their shape will come as they finish baking. Great served warm or room temperature.
Notes
Source: Food Network - I added more cinnamon than the original recipe but that was the only change.