Hazelnut meringue cake

For the meringue

Vegetable oil for greasing

hazelnuts, toasted

caster sugar

large free-range egg whites

white wine vinegar

For the PX sherry chocolate cream

dark chocolate (70% cocoa solids), broken into small pieces

pedro ximénez sherry

soft light brown sugar

double cream

To decorate

dark chocolate

Good knob of butter

toasted hazelnuts, chopped