Heat oven to 160C/140C fan/gas 3.
Oil a 23cm round cake tin, then line
the base with baking parchment.
Whizz the chocolate into small pieces
in a food processor. Tip the flour, sugar,
cocoa, oil, soured cream, eggs, vanilla,
dissolved coffee and 100ml hot water into
a large mixing bowl. Whisk everything
together with electric beaters until
smooth, then quickly stir in the whizzedup
chocolate bits. Pour the batter into
the tin and bake for 50 mins-1 hr until
risen and springy to the touch. Transfer
to a wire rack and leave to cool.
To make the icing, beat the butter in
a large bowl until light and fluffy. Add
the icing sugar, cocoa and a drop of milk,
and beat until creamy. Beat in more
milk, if necessary, to loosen the icing
to a spreadable consistency. Spread the
icing over the top of the cake and sprinkle
with crumbled Flake. The cake can be
kept in an airtight container for 1-2 days.