Preheat oven to 180°C Grease an 18cm x 28cm cake tin and line base and sides with baking paper, allowing the paper to overhang on the opposite ends.
To make the base, sift the flour and cinnamon into a bowl, then stir in the hazelnut meal and brown sugar.
Put the chocolate and butter in a small saucepan and cook over low heat until just melted. Remove from heat. When it has cooled mix it into the dry ingredients. Add the egg, mixing well.
Using the back of a spoon, press the mixture into the base of the prepared tin. Bake in oven for 15 minutes or until firm. Remove from oven, let cool to room temperature. Leave in the tin.
To make the topping, place the hazelnuts on a baking tray and bake in 180C oven for 8 minutes or until the skins start to split. Remove the hazelnuts from the oven, wrap in a clean, dry tea towel, then rub vigorously to remove the skins.
Put condensed milk, golden syrup and butter in a saucepan, and heat over a low heat, stirring, until just about to boil. Pour mixture over the cooked base, then top with hazelnuts and macadamias. Bake for 15 minutes or until the topping is firm. Let cook in the tin.
Drizzle the slice with melted dark chocolate. Once the chocolate is set, cut the slice into fingers to serve.