Begin by lining a baking sheet with parchment paper.

Unroll each thawed puff pastry sheet onto your lined baking sheet. If the pastry feels too soft, let it firm up in the fridge for 5–10 minutes before working with it. Using a pastry brush, coat the entire surface of each sheet with the melted butter.

In a small bowl, whisk together the granulated sugar, cinnamon, and nutmeg. Sprinkle the spiced sugar evenly over the buttered pastry. Starting from one side of the sheet, roll the pastry inward about halfway. Repeat from the opposite side so the two rolled edges meet in the center, gently pressing so they hold their shape.

Transfer the rolled pastry logs to a baking sheet or plate and refrigerate for 30 minutes. Once chilled, slice the pastry into thin pieces, less than ½ inch thick, and place them face-up on your lined baking sheet.

Bake at 350°F (175°C) for 20 minutes, or until the edges are golden brown and the sugar has caramelized slightly. Allow the palmiers to cool on the baking sheet for a few minutes before moving them to a wire rack to crisp up as they cool.