Preheat oven to 200deg C.
Spread hazelnuts on a baking tray and roast in oven for 5-8 minutes
to until you can smell them. If they have their skins on gently
roll them in a tea towel until their skins have come off. Roughly
chop them and set aside.
Place butter and chocolate in a saucepan and stir over a low heat
until melted and smooth.
Transfer the chocolate mixture to a large bowl and add beaten eggs,
brown sugar, sieved flour and cocoa.