Preheat the oven to 190˚C/fan oven 170˚C/gas mark 5.
To make the pastry in a food processor, put the flour, butter, sugar, egg yolks and vanilla extract into a food processor and whizz until it forms a smooth ball of dough. This may take a couple of minutes. Remove the dough from the food processor and wrap it in clingfilm. Set aside to rest in the fridge for 30 minutes.To make the pastry by hand, sieve the flour into a large mixing bowl, make a well in the centre and then pop the softened butter, sugar, egg yolks, and vanilla extract into it. Using the fingertips of one hand, squidge the butter, sugar, egg yolks and extract together until it forms a paste. Now, slowly with your other hand, start to add the flour bit by bit until it is all incorporated into the paste. Turn onto a floured board and knead together for a minute or so, then wrap it in clingfilm. Chill in the fridge for 30 minutes.
Dust a worksurface with flour and roll out the pastry to a circle big enough to line a 23cm/9in loose-based flan tin. Keep the pastry hanging over the edges. Press it firmly into the base and sides, then prick the surface lightly with a fork. Now loosely beat the egg white and brush it over the surface of the pastry – this helps to seal it. Place on a baking sheet.
Bake the pastry case for 10 minutes or until it is a light golden brown. Transfer to a wire rack to cool. When cool, remove the pastry left hanging over the edges of the tin, it should break off easily and leave the edges nice and neat. Finish trimming the edges neatly with a serrated knife. Leaving the pastry hanging over the edge before cooking prevents it from collapsing back into the tin and leaves the tin perfectly lined.
Pour the cream into a medium mixing bowl and lightly whip it. Gently stir in the yogurt and rosewater and enough icing sugar to sweeten to your taste.
Crush half the raspberries and fold them into the creamy yogurt. Spoon the filling into the pastry case. Scatter over the rest of the raspberries and chill in the fridge for 15 minutes.
Heat the raspberry jam in a small pan and gently bring it to the boil. Spoon it over the raspberries and leave to set for a couple of minutes.
Finally, scatter over some pink or red rose petals. Serve within an hour or the pastry will go soggy!