Preheat the oven to 175 °C (350 °F). Grease the bundt pan with fat and coat with breadcrumbs.
In a large mixing bowl, beat the 250 g butter with the 200 g sugar on medium speed for 3-5 minutes until light and frothy.
Add the 6 eggs one by one to the butter mixture, beating well after each addition.
In a separate bowl, combine the 250 g flour, baking powder packet, 3 tablespoons cocoa powder, and 1 tablespoon cinnamon. Sieve this mixture. Stir the sieved mixture into the butter and egg mixture until combined.
Stir in the 125 ml strong, lukewarm coffee. Fold in the 150 g coarsely chopped hazelnuts or almonds.
Pour the batter into the prepared bundt pan. Bake for 45 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool completely. Cover with chocolate icing and decorate with mocha beans.