1Mix the castor sugar and the spice, then sprinkle the mixture over the nectarines.
2Lay a sheet of puff pastry on a greased baking tray. Place the nectarines and hazelnuts down the middle with the cut sides of the fruit facing down, leaving space in between. Brush the edges with egg.
3Place the other sheet of pastry over the nectarines and nuts, and firmly press down the edges to seal.
4Brush with egg, then use a sharp knife to make parallel cuts across the top of the pastry (approximately 2,5cm apart) without cutting all the way to the edges.
5Bake in a preheated oven for 30 minutes or until the pastry is puffed and golden. Remove from the oven and leave to stand for 10 minutes, then dust with icing sugar and serve while still warm.