Put your sheet of puff pastry on a parchment lined cookie sheet. Spread Nutella on your puff pastry sheet with a spatula in a thin layer. Sprinkle with chopped hazelnuts all over.
Start rolling tightly from one side and reach the centre, repeat the same on the other side until you reach the centre. If you roll from a long side you will have mini palmiers like I did but if you roll from a short side you will end up with large palmiers.
Cover it with a plastic wrap and refrigerate for 30 minutes. Preheat oven to 425F/220C.
Take your roll out of the fridge and slice into 1/2" thickness. Place palmiers 2" apart on a cookie sheet and bake for 15 minutes until golden.
Cool on a wire rack, then dust with powdered sugar before serving.
Notes
This recipe will make approximately 30 palmiers, depending on how thickly you slice them.