Place a saucepan over a medium heat and combine the sugar and water with the vanilla pod. Bring to the boil and lower the heat to a simmer until the sugar has dissolved. Poach the sliced fresh peaches in the syrup on a low heat for 5-10 minutes or until they soften but keep their shape.
If you are using canned peaches, put contents of the 2 cans in a saucepan along with the vanilla pod. Simmer on a low heat for 5 minutes, just long enough to infuse the peaches with the vanilla flavour. Again you do not want the peaches to lose their shape.
Take off the heat, remove the peaches and reserve the syrup. Add the raspberries to the reserved syrup and let them rest in the liquid until required for the assembly.
Cut each pastry sheet in half and prick each sheet all over with a fork.
Place two rectangles of pastry on an oven tray lined with baking paper. Cover the pastry with another piece of baking paper. Weigh down the pastry with another baking tray on top. This process flattens the pastry whilst baking and results in a beautifully flaky crust.
You should be able to fit two rectangles of pastry side by side on one tray (remember to leave a small gap in between them). Unless you have multiple oven trays you will be required to do this stage in two batches.
Whip the cream until soft peaks form.
Strain the peaches and raspberries. Taste the raspberries and if you think they are a bit sharp add 1 tabespoon of icing sugar to sweeten them (Frozen raspberries might not be as sweet as fresh ones).