Roll a sheet of puff pastry to a 12" x 12" square.
Cut nine 3" x 3" squares from the pastry.
Use a cutting wheel or pairing knife to cut diagonally from the corners of each pastry square to approximately 1 inch from the center.
Place 1 tablespoon Nutella (hazelnut spread) in the center of each pastry. Sprinkle hazelnuts over the Nutella.
Fold every other point toward the center, slightly overlapping them in the middle. Press down lightly on the centers to ensure the pastry retains its shape while baking.
Brush the tops of each pastry with the whipped egg. Sprinkle with granulated sugar. Place on a a non-stick cookie sheet and bake for 16 - 18 minutes at 400 degrees F. Cool on a wire rack before serving. Dust with powdered sugar if desired.