1. Preheat the oven to 200°C (thermostat 7).
2. Unroll the puff pastry on a baking sheet lined with parchment paper. Place the chocolate spread in the center of the pastry, with the top of the spread touching the upper edge of the pastry.
3. Cut strips of pastry about 2 cm wide, starting from the spread and going towards the edge. Cut the strips slightly diagonally. Make these strips on each side of the spread.
4. Take the first 2 strips and fold them over the chocolate, crossing them. Trim any excess pastry lengthwise. Repeat this process with all the strips.
5. Seal the chocolate spread well by joining the edges of the two ends.
6. Brush with egg yolk and bake for 20 minutes.
7. It is possible to sprinkle with crushed hazelnuts, pistachios, or other nuts before baking.