01 - Preheat oven to 400°F. Line a standard baking sheet with parchment paper to prevent sticking and ensure easy cleanup.
02 - Unroll puff pastry onto a lightly floured work surface. Using a sharp knife or pizza cutter, divide the pastry into 8 equal rectangles by cutting lengthwise then crosswise.
03 - Combine dulce de leche with ground cinnamon in a small bowl, stirring until thoroughly incorporated. The cinnamon adds warmth but can be omitted if preferred.
04 - Place approximately 1 generous tablespoon of the dulce de leche mixture in the center of each pastry rectangle. Fold the pastry over to create either triangular or square pockets, then press edges firmly with a fork tines to seal completely.
05 - Transfer filled pastries to the prepared baking sheet, spacing evenly. Brush the tops generously with beaten egg using a pastry brush to promote golden browning.
06 - Combine granulated sugar and cinnamon in a small bowl. Sprinkle the mixture evenly over the egg-washed pastries, creating a sweet, spiced crust.
07 - Bake for 18 to 20 minutes until pastries are deeply golden, puffed, and crisp. The layers should be fully cooked through with visible flakiness.
08 - Allow pastries to cool on the baking sheet for 5 minutes. Serve warm for optimal texture or at room temperature. Pair with coffee or tea for a complete experience.