For the crÃ¨me pÃ¢tissiÃ¨re, fry the saffron in a dry saucepan for a few seconds then add the milk and vanilla pod. Heat the milk to scalding.
Whisk the egg yolks with the caster sugar, plain flour and cornflour. Pour over the scalded milk whisking all the time. Return to the saucepan and heat until thickened. Allow to cool.
For the sauce, combine 50ml/2fl oz water with the sugar in a saucepan and cook until the sugar has dissolved. Add the pomegranate seeds and juice, Grand Marnier and rosewater. Cook until the liquid has reduced and is syrupy. Remove from the heat and add the whole raspberries. Allow to cool.
Fill a piping bag with the crÃ¨me pÃ¢tissiÃ¨re and half-fill each courgette flower. Spoon in some pistachios and pipe in more mixture to fill the flower. Twist the end to seal.
To make the batter, put the dry ingredients into a bowl, whisk in the egg followed by the sparkling water.
Heat the vegetable oil in a heavy-based saucepan or deep-fat fryer until a breadcrumb dropped into the hot oil turns brown. (CAUTION: hot oil can be dangerous. Do not leave unattended.)
Dip each flower into the batter and deep-fry until golden-brown. Roll in the sugared cinnamon and serve with the sauce.