brandy and vanilla in a bowl. Pour on the boiling water and leave to soak for several hours or overnight.
To make the pastry
sift the flour
icing sugar and cocoa together. Add the diced butter and rub it in lightly with your fingertips until the mixture looks like fine breadcrumbs. Alternatively
do this in a food processor or a mixer and then transfer to a bowl.
Mix the egg yolk with the lemon juice and water. Use a table knife to work the liquid into the flour. Add a splash more water if you need to. When the dough begins to stick together
use your hands to gently knead it into a ball. Wrap the pastry in cling film and put in the fridge to rest for at least 15 minutes.
Preheat the oven to 200C/400F/Gas 6.
Roll out the pastry on a lightly floured surface large enough to line a 23cm/9in loose-based tart tin
3.5cm/1½in deep
leaving excess pastry hanging over the edge. Keep a little uncooked pastry back in case you need to patch any cracks later. Line the pastry with baking parchment or foil
then fill with baking beans
or uncooked rice or lentils.
Bake blind for 15 minutes
then remove the parchment and baking beans and return to the oven for about eight minutes
or until the pastry looks dry.
Use a small
sharp knife to trim away the excess pastry from the edge. Use a tiny bit of the reserved raw pastry to patch any cracks or holes if necessary. Turn the oven down to 180C/350F/Gas 4.
For the filling
put the chocolate and cream in a basin over a pan of simmering water
without letting the basin touch the water. Leave it until the chocolate has just melted
stirring from time to time. Take it off the heat and leave to cool for three minutes
then beat in the mascarpone and eggs. Use a balloon whisk to remove any lumps. Stir in the prunes and any soaking juices.
Pour the chocolate and prune mixture into the tart case. Bake for 20–25 minutes
or until almost set
with a bit of wobble still in the centre. Leave in the tin to cool completely.
