> 1 large egg
> 8 tbsp granulated or turbinado sugar, divided
> 1/4 cup cocoa powder
> 1 (17.3 oz) pkg puff pastry, thawed
> 4 tbsp chocolate-hazelnut spread, divided
In a small bowl, beat the egg with a splash of water. In another small bowl, stir 6 tbsp sugar and cocoa powder until combined.
Lightly sprinkle work surface with half of the cocoa-sugar mixture. Unfold one pastry sheet, brush with egg wash, and place egg wash–side down on sugar mixture. Coat top of dough with 2 tbsp chocolate-hazelnut spread, spreading evenly to cover completely. Roll up 2 opposite short sides to meet in the center. Wrap in plastic wrap and refrigerate for 30 min. Repeat with remaining ingredients, wrap, and refrigerate.
Preheat oven to 400°F. Line two baking sheets with parchment. Cut each puff pastry roll crosswise into 16 slices (finished cookies should be heart-shaped). Transfer to prepared pans. Sprinkle tops with remaining 2 tbsp sugar. Bake for 12 min., until golden brown and crisp. Cool completely on a wire rack. Store in airtight containers for up to 5 days.