My take on the classic Brooklyn Blackout Cake is so much easier than the original but just as delicious. The one-bowl, one-layer chocolate cake is topped with a 2-ingredient whipped ganache for an indulgent experience.
Pour the cream into a microwave-safe mixing bowl. Microwave on full power in 30-second bursts until steaming, 1 to 2 minutes total. Add the chopped chocolate and let sit for 2 minutes for the chocolate to melt. Whisk until smooth. Set the ganache aside to cool while making the cake.
Grease a 9x13-inch cake pan generously with butter or baking spray.
Add the cocoa to a large mixing bowl. Pour in the hot water or coffee and whisk until smooth and slightly thickened.
Whisk in the brown sugar, sour cream, and vegetable oil. Add the eggs and vanilla extract and whisk together. Finally, add the flour, baking soda, baking powder, and salt. Use the whisk to gently stir the batter just until no streaks of flour remain.
Pour the batter into the prepared pan and bake until a toothpick inserted in the center of the cake comes out clean, 30 to 35 minutes. Let the cake cool to room temperature in the pan set on a wire rack, about 1 hour.
When the ganache has cooled to room temperature and set to the consistency of peanut butter or Nutella, use a hand mixer to beat on medium speed until pale and fluffy, about 4 minutes. Use an offset spatula or the back of a spoon to spread the whipped ganache on the cooled cake, creating swoops and swirls. Slice and serve. Store the cake, covered tightly, on the counter for up to 3 days or in the refrigerator for up to 5 days. Love the recipe? Leave us stars and a comment below!