Chocolate: Chop the chocolate needed for the batter, set it aside. Or use white chocolate chips, chop them lightly if they are too large.
Mix: Cream the eggs and the sugar until light and thick. Add the oil and buttermilk, mix thoroughly. Mix flour, cornstarch, baking powder, and salt in another bowl. Add to the eggs together with the chocolate. Mix until just combined. Fold in the frozen berries as well.
Bake: Pour the batter into the prepared loaf tin. Bake for 40-45 minutes or until a toothpick inserted in the middle of the cake comes out clean. Let rest for about 10 minutes. Remove from the pan and let cool on a wire rack.
Ganache
Chocolate: Chop the white chocolate very finely. Place it into a small bowl.
Cream: Heat the heavy cream in a small saucepan. Make sure it’s hot but don’t let it come to a bubble. Pour over the chocolate and let sit for 1 minute.
Stir well until the mixture is smooth. If there are still some clumps in the ganache, microwave the mixture for 5 seconds, stir well again. If you still have chunks, repeat the procedure until the ganache is completely smooth. Let cool slightly until it thickens, but it’s still pourable.
Decorate: Place the rack with the loaf on a baking tray (lined with parchment paper for quick cleaning) and drizzle the ganache on top. Decorate with fresh berries. Leave to set for about 15 minutes. Slice and serve.