Preheat oven to 170C
Melt the butter, chocolate and sugar together in a large pot on low heat.
Take off the heat as soon as it is melted and add the vanilla extract.
Whisk eggs in a jug.
Mix eggs into cooed chocolate mixture
Fold in dry ingredients
Fold in hazelnuts
Cook for 45 to 50 mins
Remove from oven
Leave to cool in pan
Once cool slice and dust with icing sugar.
Serve with coffee and tea