1 head white radicchio, leaves torn into bite-sized pieces
150²µ/5½´Ç³ú shallots, finely chopped
sea salt flakes and freshly ground black pepper
75²µ/2¾´Ç³ú caster sugar
125²µ/4½´Ç³ú currants
3 tbsp hazelnuts, roasted
4 tbsp olive oil
120ml/3¾fl oz extra virgin olive oil
375ml/13fl oz white wine vinegar
2 whole mackerel, butterflied
150ml/5fl oz white wine