If using frozen puff pastry, thaw for 20 to 30 minutes before rolling it out.
When ready to roll out, preheat oven to 400°F. Generously butter two baking sheets.
Flour your counter, as well as the rolling pin. Roll out both puff pastry sheets gently to about 9- or 10-inches by 11-inches. Cover them entirely with the sugar, as evenly as you can. Then, roll again with the rolling pin, with the purpose of not making the sheets larger or bigger but setting the sugar in the puff pastry.
Cut the sheets into rectangles of about 3- by 5-inches with a knife. You should have 12 chubby rectangles.
Place the campechanas on the baking sheets. Position rack in the upper third of the oven. One batch at a time, bake for 7 to 8 minutes at 400°F, then raise the oven temperature to 500°F and bake for an additional 4 to 5 minutes. Just until all sugar has melted and caramelized. Don’t let any extra minutes go by, or the caramel will burn and turn bitter.
Repeat with the other batch. Once cooled completely, cover so they will stay crisp.