Preheat your oven to 400°F (200°C).

Unroll the thawed puff pastry sheet onto a lightly floured surface.

In a small bowl, mix together the cocoa powder and granulated sugar.

Sprinkle the cocoa powder mixture evenly over the entire surface of the puff pastry sheet.

Starting from one long side, tightly roll the pastry sheet towards the center until it reaches the middle.

Repeat with the other long side, rolling towards the center until the two rolls meet.

Slice the rolled pastry into 1/2 inch thick slices.

Place the slices onto a lined baking sheet and brush them with the melted chocolate.

Bake in the preheated oven for 12-15 minutes or until golden brown and crispy.

Remove from the oven and allow to cool completely.

Dust the palmiers with powdered sugar before serving.