To make the pastry, place the flour, butter and sugar into a bowl. Gently and quickly rub the ingredients together into the consistency of bread crumbs (or you can use a food processor to blend to the same consistency). Lightly beat the egg yolk and drizzle it into the flour crumbs. Use a knife to mix through until the crumb starts to come together. If the mixture is too dry you can add small amounts of egg white to the bowl or processor and blend till the crumb comes together.
Using your hands flatten the dough to about 2cm/1in thick. Wrap in cling film or grease proof paper and refrigerate for 30 minutes.
Grease a 25cm/10in tart tin with butter and leave the tin to chill in the fridge.
When you are ready to roll out the pastry, remove the pastry from the fridge and place between two large sheets of cling film. Roll out with a rolling pin until 3mm (1/8 inch) thick and until the circle formed is big enough the line the base and side of the tart tin.
Remove the top layer of cling film. Take the cooled tart tin from the fridge. Slide your hand palm up under the bottom layer of cling film with the pastry on top. Flip the pastry over onto the tart tin and gently lower into the base and using your thumb. Lightly push into the edges. Then use your thumb to “cut” the pastry along the rim of the tin. Remove the cling film and prick the pastry base with a fork. Chill the pastry and tin in the fridge while you heat the oven.
Preheat the oven to 180C/350F/Gas 4
To blind bake the pastry, remove the pastry and tart tin from the fridge. Cut a piece of greaseproof paper or baking parchment that is larger than the tin and scrunch into a ball and open out again so that it’s soft and less rigid. Place the paper into the pastry case and gently fill with dried pulses or baking beans. Blind bake the pastry case in the oven for around 15-20 minutes, until it feels dry to the touch. Remove the parchment/greaseproof paper and beans, brush the pastry with egg white and return to the oven for 5-8 minutes to seal the pastry.
To make the pastry cream, place the egg yolks and caster sugar in a bowl. Whisk until thick and pale in colour then stir in the flour and add a pinch of salt.
Place the milk in a saucepan, take the vanilla pod and score down the length with a knife add the pod to the milk and bring to the boil. Remove from the heat and leave the mixture to infuse for 10 minutes.
Remove the vanilla pod and then slowly add the hot milk to the egg mixture, whisking all the time. Pour the mixture back into the pan and reduce the heat to low. Whisk constantly and bring to the boil again. After around two minutes the mixture should thicken. Pour into a cold bowl to stop the cooking process.
Whisk the cream until soft peaks form when the whisk is removed. Add the vanilla extract and sugar and mix them in. Then fold the cream into the pastry cream mixture and chill.
To assemble the tart, spoon the cooled pastry cream into the pastry case and top with raspberries. Dissolve the redcurrant jelly into the just boiled water to make a glaze. Using a pastry brush, gently coat the raspberries with the glaze.
To serve remove the outer ring of the tin. Ease the base off with a knife and slide onto a plate or cake stand.