Palmier cookies with cocoa

Ingredients:

• 4 tablespoons unsalted butter at room temperature
• 1 tbsp. + 3 tbsp. sugar
• 2 tablespoons cocoa powder
• 2 tbsp. breadcrumbs
• 1 large egg yolk
• 1 teaspoon ground cinnamon
• 1 teaspoon premium flour
• 1 sheet frozen puff pastry (half a 500g package), thawed

Preparation:

1. Position oven racks in the upper and lower thirds of the oven and preheat to 220°C (425°F). Line 2 baking sheets with parchment paper.
2. In a food processor, combine butter, 3 tablespoons sugar, cocoa powder, breadcrumbsCombine the egg yolk, cinnamon, and flour and whisk until smooth. Spread the remaining 1 cup of sugar on a clean work surface. Unfold the puff pastry and place it on top of the sugar, pressing gently to coat. Flip it over and press the other side down, then roll out the sheet into a 12-inch square.
3. Spoon the cocoa mixture onto the puff pastry in mounds and spread it into a thin, even layer. Using your fingers, fold one side toward the center, then fold the opposite side toward the center until they meet. Trim the short ends with a knife. If the folded dough is soft, refrigerate it until it hardens.
4. Slice the dough roll crosswise into 1-cm-thick slices and place cut-side down on the prepared baking sheets, spacing them about 5 cm apart. Bake until golden brown and crisp on the bottom, 4-6 minutes. Flip with a thin spatula, switch the baking sheets, and continue baking until golden brown on the other side, another 4-6 minutes. Let the cookies cool on the baking sheets for 1 minute, then transfer them to wire racks to cool completely.