Pre-heat oven to 400°F, and line a cookie sheet with parchment paper.
Sprinkle sugar on your rolling surface.
Roll out puff pastry sheets, using a rolling pin to make each sheet about the size of a cookie sheet.
“OG” Palmiers: Spread half the melted butter on one of the puff pastry sheets, and then sprinkle half of the sugar on top. Sprinkle some colored-sugar as well, if you like. Lay the second puff pastry sheet on top of the first and cover with remaining butter and sugar. Optional: add some colored sugar.Fruity Palmiers: Spread a thin layer of jam on one of the puff pastry sheets. Lay the second puff pastry sheet on top of the first and cover with another thin layer of jam.Choco-Palmiers: Sprinkle a thin layer of Hagelslag/chocolate sprinkles on one of the puff pastry sheets (or spread Nutella). Lay the second puff pastry sheet on top of the first and cover with another thin layer of sprinkles or Nutella. Take the shorter ends of the layered puff pastry sheet, and roll both in to meet in the middle.
Once the two sides have been rolled up, lightly press them together.
Wrap the roll in cling wrap, and place it in the freezer for 30 minutes or in the refrigerator for one hour.
Use a sharp paring knife to cut the pastry into 1/3" slices. (I find they keep their shape best if you have the log facing upside down as you cut). Lay slices flat on lined cookie sheet with a good amount of space in between each, they will expand in the oven.
Sprinkle the tops with sparkling sugar (if you have it) or regular sugar.
Bake for 8 minutes before flipping them over and baking for an additional 4 minutes. Pro tip: they'll flip over easier if you make sure the tops are starting to get a little golden first.