Preheat your oven to 200 degrees and cover two baking trays with baking paper.
Break the egg into a small bowl and lightly whisk before setting aside until needed.
Place one piece of slightly thawed puff pastry onto your bench. Cut it in half lengthways and then cut each half diagonally, so that you end up with four rectangles per sheet of pastry. Continue to cut each sheet of pastry until you have 12 rectangles.
Brush the two long edges with the beaten egg, and place a heaped teaspoon of Nutella in the middle of the base of the triangle.
Beginning at the short end (the one with the Nutella) roll the pastry up and gently bend the centre of the rolled pastry to give it a curved ‘croissant’ shape.
Continue until all rectangles have been rolled and bent, then place on a baking tray and brush with the beaten egg.
Bake for 12 – 15 minutes or until golden.