For the Pastry:
Place flour, icing sugar, salt and butter into a mixing bowl and with your hands rub the butter into the flour until it resembles coarse breadcrumbs.
Add the egg yolk to the mixture and work it into the flour/butter mix to form a dough.
Tip the dough out onto a work bench and briefly knead until the mixture comes together and there are not butter lumps in the dough.
Wrap the dough in cling film and place in the fridge to chill completely for 45 minutes.
Line the base of a spring-form tin with baking paper and butter and flour the sides, or if using a tart base butter and flour the tart and set aside.
Once the pastry is chilled remove from the fridge and work the pastry on a lightly floured bench until soft enough to roll but still cold.
Roll the pastry out to 1cm thickness and use a dinner plate to cut a circle out of the pastry 4cm larger than your tin or tart base.
Carefully place the pastry into the tart base and return the lined tin or tart base to the fridge to rest for 20 minutes.
Once rested remove from the fridge and bring the pastry up to room temperature.
Line the pastry or tart tin with foil and pour over rice or pastry weights. Place the tart base into a pre-heated oven combi setting 160°C for 25-30 minutes until golden brown.
If the pastry has not browned on the bottom remove the pastry weights and bake for 5 further minutes with the weights.
Once cooked place the pastry on a cake rack to cool
For the Filling:
Set the oven to 100°C steam setting and cover the chocolate with clingfilm and place the chocolate in the oven to partially melt for 10-15 minutes.
In a small saucepan pour the cream and milk and place it on the stovetop over medium heat and bring it to the boil.
Crack the eggs into a mixing bowl and briefly whisk. Once the cream and milk mixture has boiled remove from the stove and pour the beaten eggs into the milk mixture and whisk together.
Remove the chocolate from the oven and re-set the oven to the highest dry temperature possible 250°C is ideal.
Pour the milk, cream and egg mixture into the partially meted chocolate and whisk together until glossy and smooth.
Pour the chocolate mixture into the baked tart base and place the tart on a flat baking tray.
Once the oven has reached temperature turn the oven off and place the tart into the oven. Leave the tart un-disturbed for 25-30 minutes before you check.
After 25-30 minutes open the oven door and give the baking tray a slight shake, if the tart is set but has a slight wobble in the middle it is ready to remove.
Place the tart on a cooling rack and leave to cool to room temperature, approx 2-3 hours.
Serve the tart in wedges at room temperature with double cream and chocolate shavings.