Preheat the oven to 200C/400F/Gas 6. Grease a 24cm/10in tart tin with butter.
Roll out the shortcrust pastry onto a lightly floured work surface to a 0.5cm/¼in thickness. Line the prepared tart tin with the pastry. Prick the pastry several times with a fork, then chill in the fridge for 30 minutes.
When the pastry case has rested, place a sheet of baking parchment into it and half-fill with baking beans. Transfer the pastry case to the oven and bake for 15 minutes, or until pale golden-brown.
Remove the baking parchment and baking beans and return the pastry case to the oven for a further 4-5 minutes, or until pale golden-brown.
Spread the raspberry jam onto the pastry base in an even layer. Sprinkle over the three tablespoons of non-toasted desiccated coconut and half of the fresh raspberries. Set the pastry base aside.
Bring the milk, vanilla pod and vanilla seeds to the boil in a pan, then reduce the heat to a simmer and simmer for 1-2 minutes. Remove the vanilla pod (it can be cleaned thoroughly and reused in another recipe).
In a bowl, beat together the egg yolks and sugar until well combined.
Pour the hot milk and vanilla mixture over the egg and sugar mixture, whisking continuously, until the mixture is smooth and well combined.
Return the mixture to the pan over a medium heat. Whisk in the cornflour, a tablespoon at a time, until well combined, then heat, stirring continuously until the mixture is thick enough to coat the back of the spoon.
Transfer the custard mixture to a clean bowl and dust with the icing sugar (this prevents a skin from forming on the surface of the custard). Set aside to cool, then chill in the fridge for 30 minutes.
Whisk the whipped double cream into the chilled custard mixture until well combined.
Spoon the custard and cream mixture into the pastry case in an even layer. Sprinkle over the remaining fresh raspberries.
To serve, sprinkle over the three tablespoons of toasted desiccated coconut. Serve immediately.