1. Pre-heat the oven at 200 °C.
2. With the help of a ring mold cut the puff pastry into 4 circles (ø cm 8).
3. Mix egg and brush it on top of each. Sprinkle with granulated sugar.
4. Place the circles in the oven at 210 °C for about 18 minutes.
5. Pour the cold cream in the bowl of a food processor and whisk cream until stiff.
6. Add to the custard cream the whipped cream and lightly mix to marbleize.
7. Cut the circles longitudinally and stuff with whipped custard cream, chestnuts and dark chocolate flakes.