Heat oven to 180C/160C fan/gas 4.
Grease and line a 20 x 30cm rectangular
cake tin with baking parchment – the
best way to do this is with 2 long strips
of parchment. Put the ingredients for
the base in a food processor and blitz
until it starts to clump together – don’t
worry if the peanuts are still a little
chunky, they will add a lovely texture.
Tip onto your work surface and knead
briefly to bring together as a dough.
Press the dough into the base of your
tin in an even layer. Bake for 25 mins
until golden, then set aside to cool.
To make the peanut butter layer, melt
the butter and peanut butter in a small
pan and mix until smooth. Sieve the
icing sugar into a bowl, then pour in the
hot butter mixture and stir to combine.
While the mixture is still warm, pour over
the base and smooth out with a spatula.
Chill for 2 hrs until set.
To make the caramel layer, put the
caramel and salt in a pan, bring up to the
boil and simmer vigorously for 2-3 mins,
whisking continuously, until the colour
darkens a shade or two and the caramel
thickens slightly. Leave the caramel to
cool for 20 mins (see tips, below).
Once cooled, pour it over the peanut
butter layer and return to the fridge for
a further 2 hrs.
Melt the chocolate in a heatproof bowl
set over a pan of barely simmering water.
Meanwhile, put the toffees and the milk
in a small saucepan and gently heat. They
will clump together and struggle to melt
at first, but keep heating and eventually
they will turn into a runny toffee sauce.
Remove the tin from the fridge and
pour the chocolate over the salted
caramel layer, tipping the tin to spread
the chocolate over the surface. Use a
spoon to quickly drizzle the caramel over
the chocolate in a thin loopy pattern (or
see tip, below). If the toffee starts to get
too thick, add a splash more milk or
cream and pop it back on the heat until
runny. Sprinkle over the sea salt flakes
and put the tin back in the fridge to chill
for 2 hrs before slicing.