Mix the grated hazelnuts, sugar, breadcrumbs, cocoa powder and cinnamon together well. Gradually add the boiling milk until you have a spreadable mixture. The nut mass can be very soft at first, the crumbs soak up a lot of liquid. Let it cool down and refine it with a dash of rum if necessary.
You can mix hazelnuts, almonds and walnuts well. Using walnuts alone is not recommended, it gives a very intense aroma - almonds alone give a very fine body.
This amount of nut filling is enough for a large plait made from 1/2 kg of flour.