01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - Unroll puff pastry on lightly floured surface. Cut into 8 equal rectangles, approximately 3x4 inches each.
03 - Combine dulce de leche and cinnamon in small bowl. Stir until thoroughly incorporated.
04 - Place 1 generous tablespoon dulce de leche mixture in center of each pastry rectangle. Fold dough over to form squares or triangles. Press edges firmly with fork to seal completely.
05 - Transfer filled pastries to prepared baking sheet. Brush tops generously with beaten egg.
06 - Mix granulated sugar and cinnamon in small bowl. Sprinkle evenly over egg-washed pastries.
07 - Bake 18 to 20 minutes until pastries are golden brown and puffed. Rotate baking sheet halfway through for even browning.
08 - Cool on baking sheet for 10 minutes. Serve warm or at room temperature.