Preheat the oven to 200°C (400°F). Lay one sheet of puff pastry flat on a sheet of baking paper and spread the chocolate hazelnut spread evenly across the surface, leaving a 1-centimetre border around the edges. Place the second sheet of puff pastry on top of the first, aligning the edges, and gently press down to seal the layers together.

Using a sharp knife, cut the pastry into the shape of a Christmas tree, trimming away the excess pastry around the edges (see step-by-step photos in the post for more detail of what this step should look like). Save the scraps for cutting a star for the top and making mini twists / decorations. Starting from the bottom, cut horizontal slits on both sides of the tree, leaving a solid “trunk” in the centre. Make each branch about 1.5 to 2 centimetres wide.

Carefully twist each branch a few times to create a spiral effect. Cut a star from the scraps and use a little of the beaten egg to stick it to the top of the tree. Brush the tree with the egg. Transfer the tree carefully on the baking paper to the baking tray and bake for 20-30 minutes, or until the pastry is puffed and golden brown.

Optionally, dust the Christmas tree with icing sugar to finish. Serve immediately.