Preheat the oven to 160°C

Melt butter and chocolate together over a bain marie

Whisk together eggs, sugar, maple syrup and honey

Pour melted chocolate and butter into egg mixture and whisk

Fold in sifted flour, cocoa powder, salt and hazelnuts

Line a tray with baking paper and pour in mixture

Bake for 20 minutes then turn tray and bake for a further 8 minutes

Allow to cool for 30 minutes before slicing