Start off by preheating your oven to 180 degrees Celsius. Grease a rectangular tin with dimensions of roughly 35x24cm with a little melted butter and line the bottom and sides of the tin with greaseproof paper which has been cut to size to ensure a good fit. Smooth the paper down and brush over some more melted butter.

Beat together the butter and sugar until pale and fluffy before adding in the eggs, one at a time, beating well between each addition.

Sift in the flour, cocoa powder and baking powder and fold in to create a smooth batter. Transfer to the baking tin and spread out to evenly cover the tin and reach the corners. Place into the preheated oven and bake for about 15-18 minutes, until a skewer stuck into the cake comes out clean.

Remove from the oven and allow to cool for 10 minutes in the tin before turning out onto a wire rack and allowing to cool completely before applying the ganâche.

While the cake is baking heat the cream for the ganâche in a pan until almost boiling. Remove from the heat and break the chocolate into small chunks and place into the hot cream. Stir constantly until the chocolate has completely melted and blended with the cream to form a smooth ganâche. Transfer to a bowl and store in a cool place until it has set a little and taken on a more spreadable consistency.

Once the cake is cool, cut it down the middle to create two evenly sized rectangles. Spread ganâche onto one, going right up to the edges and then arrange about 80% of the blueberries on top of the ganâche.

Place the other half of the cake on top to sandwich the blueberries and then whip the cream for the topping until stiff. Transfer to a piping bag and pipe whipped cream all over the top of the cake, as well as the gap where the two halves were sandwiched together.

Arrange more blueberries on top and finally take the 50g of plain chocolate for the topping. Pull a sharp knife across the underside of the chocolate to create shavings and sprinkle on top. Serve and enjoy!