Preheat the oven to 180 C / Gas 4. Grease and line a 900g loaf tin with baking parchment.
Measure then lay 100g hazelnuts out on a baking tray (reserving 30g for the topping).
Bake the hazelnuts in the preheated oven for 10 to 15 minutes, or until golden brown. Remove from the oven and allow to cool slightly. Blend in a food processor until they resemble fine breadcrumbs and set aside.
In a large bowl, combine the butter and sugar and beat until smooth with an electric whisk. Add the eggs, one at a time, beating well after each addition. Sift in the flour then add the ground hazelnuts, baking powder, milk, cocoa powder and vanilla extract. Beat until well blended and light. Transfer to the prepared loaf tin.
Bake in the oven for 80 to 90 minutes, until a skewer inserted into the centre comes out clean. Remove from the oven and allow to cool fully. Once cooled, spread the chocolate hazelnut spread on top then sprinkle with the remainder of the hazelnuts. Serve.