1. Preheat the oven to 400°F.
2. Sprinkle half of the powdered sugar on the work surface.
3. Roll out the pastry into a 20 x 30 cm rectangle. Sprinkle the rectangle with powdered sugar.
4. Fold the 2 large sides of the rectangle towards the middle. Sprinkle with sugar and fold the edges towards the middle again, leaving a 0.5 cm space in the center.
5. Fold the pastry in half onto itself to form a large bun.
6. Refrigerate for 30 minutes.
7. Cut the pastry bun into 1 cm thick slices. Brush with egg yolks. Place on a baking sheet lined with parchment paper, leaving space between them.
8. Cover one side of each palmier with grated coconut.
9. Bake for 6 minutes.
10. Remove from the oven, turn the palmiers over. Cover with grated coconut and return to the oven for 5 minutes.
11. Remove from the oven and serve.