Preheat the oven to 180'C.
Melt the chocolate in a heatproof bowl over simmering water (bain-marie).
Sift the flour, baking powder and cocoa powder together.
In a bowl beat the sugar and the butter together until the mixture is pale and fluffy. Beat the eggs into the butter mix one at a time. Gently incorporate the oil into the butter mix. Gently fold the flour mix through the butter, then the melted chocolate and finally the chopped hazelnuts.
Pour the mixture into a cake tin and bake for 30-40 minutes.
After about 30 minutes check the cake with a skewer. If it comes out clean it is ready.
Allow the cake to cool in the tin.
Boil the cream and the golden syrup together. Whisk in the cocoa powder. Bring the mixture back to the boil and simmer for 3 minutes. Allow to cool slightly.
Remove the cake from the tin and place on a cooling rack. Pour the icing over the cake and make sure it is completely covered.
«The chocolate icing should be cold enough before pouring over the cake but still runny. The consistency should be of a thick batter.»