Place the flour and icing sugar in a food processor, and pulse briefly to mix.
Add the cold butter, roughly chopped, and pulse until the mixture resembles breadcrumbs.
Add the egg yolk, along with 1 tbsp of cold water. Pulse until the dough has almost come together.
Tip everything out and bring the pastry together by hand. Shape into a flat disc and wrap in cling film, then chill in the fridge for at least 30 minutes.
On a piece of baking parchment, roll out the pastry into a circle, slightly larger than the tart tin, and about 3mm thick. Lift up the baking parchment and invert over the tart tin. Peel back the baking parchment.
Carefully lift up the edges, and ease the pastry down into the tin.Push and press the pastry into every crease of the tin, leaving a small lip over the side of the tin.Patch areas where required, trying to keep the pastry the same thickness.
Move the tart tin to the fridge for 20 minutes, or to the freezer for 5 minutes.
Preheat the oven to 180c/160c fan
Use a paring knife to trim the pastry, flush against the top of the tart tin.
Prick the base of the tart shell with a fork, and then line the tart with ovenproof clingfilm or baking parchment, and fill with uncooked rice.
Bake the tart shell for 20 minutes, then lift out the rice parcel. Bake for another 10-12 minutes, until the pastry is completely cooked.
Leave the tart shell to cool completely and dry out. Remove from the tin, and place on the presentation plate.
Soak 4 gelatine leaves in cold water.
Slice open the vanilla pod, and scrape out the vanilla beans.In a saucepan, warm the double cream, whole milk, sugar, and vanilla beans, until steaming hot.
Wring the water out of the gelatine leaves, and whisk into the hot cream mixture, and then sieve everything into a heatproof jug.
When the panna cotta mixture is almost at room temperature, place the tart shell inside the fridge, and pour in the panna cotta.
Leave to set up for at least 2 hours before adding the jelly. Test for set by jiggling the plate slightly, rather than poking it with your finger!
Summer berry jelly
Soak 2 gelatine leaves in cold water.
Place the water, your berries of choice, and the caster sugar into a saucepan. Bring to the boil, and then use a wooden spoon to break up the berries a little.
Sieve the jelly into a heatproof jug, pressing down on the pulp to extract all the juice and flavour from the berries.
When the jelly is almost at room temperature, pour carefully on top of the panna cotta, filling the tart as much as you safely can.
Leave to set for at least an hour before adding decoration. Test for set by jiggling the plate slightly, rather than poking it with your finger!
Decorate the tart with some more of the summer berries and a few sprigs of mint. Store in the fridge until ready to serve.