1 sheet puff pastry frozen thawed half of a 17-ounce box
1 cup sugar
4 tablespoons butter unsalted at room temperature
2 tablespoons cocoa powder unsweetened
Equipment
food processor
baking sheet
baking paper
oven
knife
spatula
Directions
Position racks in the upper and lower thirds of the oven and preheat to 425 degrees F. Line 2 baking sheets with parchment paper.
Pulse the butter, 3 tablespoons sugar, the cocoa powder, breadcrumbs, egg yolk, cinnamon and flour in a food processor until smooth.
Spread the remaining 1 cup sugar on a clean surface. Unfold the puff pastry and set it on top of the sugar, pressing gently to coat. Flip and coat the other side, then roll out the sheet into a 13-inch square.
Drop mounds of the cocoa mixture onto the puff pastry and spread in a thin, even layer. Using your fingers, roll 1 side of the pastry into the center, then roll the opposite side into the center to meet it. Trim the short ends with a knife. (If the rolled-up dough is soft, refrigerate until firm.)
Cut the dough roll crosswise into 1/2-inch-thick pieces and arrange cut-side down, about 2 inches apart, on the prepared baking sheets.
Bake until golden and crisp on the bottom, 4 to 6 minutes; flip with a thin spatula, switch the position of the pans and continue baking until golden on the other side, 4 to 6 more minutes.
Let cool 1 minute on the baking sheets, then transfer to racks to cool completely.
