01 -
Place the heavy cream in a microwave-safe mixing bowl and heat in 30-second intervals until steaming, approximately 1 to 2 minutes. Add chopped chocolate and let stand for 2 minutes to melt. Whisk until completely smooth, then set aside to cool at room temperature.
02 -
Preheat the oven to 175°C. Generously grease a 23x33-centimetre cake pan with butter or baking spray.
03 -
In a large mixing bowl, combine unsweetened cocoa powder with hot water or coffee. Whisk until the mixture is smooth and slightly thickened.
04 -
Whisk the brown sugar, sour cream, and vegetable oil into the cocoa mixture. Add the eggs and vanilla extract, whisking until uniform. Incorporate the flour, baking soda, baking powder, and salt, gently stirring until no dry streaks of flour remain.
05 -
Pour the batter evenly into the prepared cake pan. Bake for 30 to 35 minutes until a toothpick inserted in the centre comes out clean.
06 -
Place the pan on a wire rack and allow the cake to cool to room temperature, approximately 1 hour.
07 -
Once the ganache has cooled and thickened to a spreadable consistency, whip it with a hand mixer on medium speed for about 4 minutes until pale and fluffy.
08 -
Spread the whipped ganache evenly over the cooled cake using an offset spatula or the back of a spoon to create decorative swirls. Slice and serve.