01 -
Preheat the oven to 350°F (177°C). Grease and line two 8-inch round cake pans with parchment paper.
02 -
In a large bowl, whisk together all-purpose flour, black cocoa powder, unsweetened cocoa powder, baking soda, baking powder, and salt until fully combined.
03 -
In a separate bowl, combine granulated sugar, dark brown sugar, and vegetable oil. Whisk until thoroughly blended. Add eggs, one at a time, then mix in the vanilla extract, buttermilk, and sour cream.
04 -
Gradually incorporate the dry ingredients into the wet mixture, mixing just until combined.
05 -
Slowly pour in the hot coffee and mix until the batter is smooth and even. Avoid over-mixing.
06 -
Divide the batter evenly between prepared pans. Bake for 25 minutes, or until a toothpick inserted in the center emerges clean. Allow cakes to cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.
07 -
In a saucepan over medium heat, whisk together granulated sugar and flour, then slowly add milk while whisking to avoid lumps. Cook, stirring frequently, until the mixture thickens, about 5 to 8 minutes. Remove from heat and cool to room temperature.
08 -
In a stand mixer, beat the unsalted butter until smooth and fluffy. Gradually add the cooled milk mixture, beating until light and airy. Mix in vanilla extract and salt until incorporated.
09 -
Place one cake layer on a serving plate. Spread a generous amount of frosting over the first layer. Top with the second cake layer, then cover the entire cake with the remaining frosting. Smooth the surface with an offset spatula.