Preheat oven to 200ºC (390ºF). Cut out 4 x 12cm squares from the pastry. Place on a baking tray lined with non-stick baking paper. Cut the rhubarb into 12cm lengths. Place the rhubarb and sugar in a bowl and toss to combine. Divide the crushed biscotti between the pastry squares and top with the rhubarb. Brush the edges of the pastry with the egg. Bake for 15 minutes or until the pastry is golden and the rhubarb is soft. Dust with the icing sugar and serve with the cream. Serves 4.