Preheat the oven to 200C/400F/Gas 6.
Heat the sugar in a small ovenproof frying pan until melted. Add the vanilla pod and cook until the sugar is a deep caramel colour. Add the orange segments and stir to coat. Remove the vanilla pod (it can be used again in another dish).
Place the egg whites and melted butter into a bowl and mix well. Brush this mixture over each sheet of pastry. Scrunch up the pastry sheets and place on top of the caramelised orange mixture.
Transfer to the oven and bake for 5-6 minutes, or until the pastry is crisp and golden-brown.
To serve, place the croustade into a serving dish.