Thaw one half sheet of the puff pastry according to the package instructions. While the pastry is thawing, process the pistachio into a powder with a food processor.

Pistachio and brown sugar filling: combine the pistachio powder and the brown sugar in a small bowl and set aside.

Spread the raw sugar onto a clean work surface. Carefully unfold the sheet of puff pastry onto the sugar. Roll out the sheet of puff pastry into a 10-by-12-inch rectangle. (You can divide the sheet of dough into two equal parts, and you will have two 10 by 6). When you divide the dough, divide the brown sugar pistachio filling mixture between the two rolled pastries

Brush the dough with the butter and sprinkle the pistachio filling onto the butter. Roll one side of the pastry inward to the center. Then roll the opposite side of the pastry towards the center to meet and press lightly to join. Wrap the roll dough in a cling film or parchment paper and place in the refrigerator to firm back up for about 5 - 10 minutes.

Preheat the oven to 350 F / 108 C. Prepare the baking sheet with parchment paper or silicone mat.

Unwrap the dough, trim the ends of the rolled pastry to get a straight edge on both sides. Cut the rolled pastry into ½-inch thick pieces. Arrange cut side down, about 2-inches apart onto the prepared baking sheet.

Flatten slightly and bake them in the preheated oven for about 10- 15 minutes, or until puffed and golden brown.

Remove from the oven and cool for about 5 minutes in the baking pan then transfer them to a cooling rack to cool completely.

Serve and enjoy.