To make the pastry, whizz the
hazelnuts in a food processor until finely
ground. Add the flour, icing sugar and
butter, and pulse until the mixture
resembles breadcrumbs. Add the egg
yolk and 1-2 tbsp cold water, and pulse
until the dough comes together. Tip the
dough out and flatten into a disc, then
wrap in cling film and chill for 30 mins.
Heat oven to 180C/160C fan/gas 4.
On a floured surface, roll out the pastry
to line a 23cm loose-bottomed, deep
tart tin. Trim the edges and prick the
base with a fork, then line with baking
parchment and fill with baking beans.
Bake for 20 mins, then carefully remove
the baking beans and parchment and
bake for a further 5-10 mins until light
golden. Allow to cool.
Meanwhile, make the salted caramel.
Tip the sugar into a small pan, add
1-2 tbsp water and heat gently to dissolve
the sugar. Increase the heat and cook
until the sugar turns to an ambercoloured
caramel. Reduce the heat and
add the butter, cream and golden syrup,
and stir until the sauce is smooth and
thickened. Remove from the heat and
add the salt. Allow to cool for a few mins,
then spread onto the tart base. Scatter
with chopped hazelnuts and set aside.
For the chocolate filling, melt the
chocolate and butter in a heatproof bowl
set over a pan of simmering water. Stir
until smooth, then remove from the heat
and allow to cool slightly. In a separate
bowl, whisk the eggs, egg yolk and caster
sugar for about 6 mins until thick and
pale. Fold in the melted chocolate and
cocoa, then pour into the tart case.
Transfer to a baking sheet and cook for
20-25 mins or until set and the top has
formed a crust. Allow to cool to room
temperature before serving in slices.