Grease an 11.8-inch loaf tin with butter, dust it with unsweetened cocoa powder, and preheat the oven to 356°F.

Toast the ground hazelnuts in a pan without oil and let them cool for a few minutes. This enhances their nutty flavor.

In a bowl, mix the plain flour with baking powder and ground cinnamon. Cut the dark chocolate into chunks.

In another bowl, use a whisk or hand mixer to beat the butter and sugar until creamy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the flour mixture to the butter mixture, alternating with the cream. Mix until all the flour and cream are incorporated. Fold in the toasted hazelnuts and chopped chocolate.

Pour the batter into the prepared loaf tin and bake for about 60 minutes. To check for doneness, insert a wooden toothpick near the center of the cake. If it comes out clean, the cake is ready.

Let the cake cool briefly in the tin, then remove it and allow it to cool completely. Dust with powdered sugar, drizzle with icing, or glaze with chocolate before serving. Enjoy!