1. Preheat the oven to 350°F (180°C). Line a 9×5 inches (23x12cm) loaf tin with baking parchment and grease lightly. Set aside.

 

2. Add the butter, both sugars, and half of the chocolate to a small pot and heat up until butter and chocolate are melted and well combined. Remove from the heat and let cool down. You can also do that in the microwave.

 

3. Add the eggs, sour cream, milk, and vanilla extract to a large bowl and mix until well combined. Add the cooled chocolate mixture and mix until well incorporated. Mix the flour with cocoa, ground hazelnut, hazelnut brittle, baking powder, baking soda, and salt and add to the large bowl – mix until just combined. Add the remaining chopped chocolate and fold in. Pour the batter into the prepared loaf tin, smooth out the top and bake for 55-60 minutes or until a wooden skewer inserted into the center comes out (almost) clean. Take out of the oven and let cool down in the tin for some time, then remove carefully and let cool down completely on a wire rack.

 

4. For the topping chop the chocolate and add together with the sour cream and sugar to a microwave-safe bowl and heat up gently until the chocolate has melted. Stir to combine. Add the hot water and mix in. Decorate the cake with the cream and sprinkle with some hazelnut brittle. Let cool before slicing.