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.
03 - Mix dulce de leche with cinnamon in small bowl if using.
04 - Place 1 generous tablespoon dulce de leche in center of each rectangle. Fold pastry over forming squares or triangles. Press edges firmly with fork to seal.
05 - Arrange sealed pastries on prepared baking sheet. Brush tops with beaten egg.
06 - Mix sugar and cinnamon together. Sprinkle evenly over pastries.
07 - Bake for 18-20 minutes until golden brown and puffed.
08 - Cool briefly on baking sheet. Serve warm or at room temperature.