Pre-heat oven to 140°C (fan forced 120° C); 280°F/ 240°F. Lightly grease and line a 23cm/9in spring form pan.
In a large saucepan combine dark chocolate, brown sugar and sour cream. Gently heat over a low heat, stirring occasionally until completely melted (do not let the mix boil).
Soften the Copha in a microwave and add to the mixture, stirring until well combined. Remove from heat and transfer mixture to a large mixing bowl, leaving to cool for 20 minutes.
Once cooled, add eggs one at a time to the mixture, whisking between each addition until well combined.
Combine plain flour, baking powder and cocoa powder together and sift over chocolate mix, stirring through until well combined. Pour mix into the prepared pan, baking in the middle of the oven for 1-1 ½ hours or until a skewer is inserted and shows moist crumbs sticking to it.
Remove cake from oven. Set aside in the pan for 10 minutes before turning onto a wire rack for 30 minutes or until cooled completely.
In a medium sized saucepan, bring cream to boil over medium heat
Remove from heat, add chocolate and stir until combined and glossy. Set aside to cool
To assemble spoon ganache mixture into a piping bag fitted with a 1.5cm fluted nozzle. Pipe rosettes over the top of the cake. Allow ganache to set.
Tips & Hints:
Serve with pouring cream. If refrigerated, bring to room temperature before serving. Can be stored in an air-tight container in the fridge for up to 3 days.