Step 1

Preheat the oven to 325°F and spray two 9-inch light-colored aluminum cake pans with nonstick baking spray with flour. Set aside.

Step 2

In the bowl of a mixer, combine the cake mix, flour, salt, sugar, and cocoa powder until well mixed. Add the hot coffee and mix to combine.

Step 3

Add the melted butter, oil, and sour cream, mix to combine. Scrape down the sides of the bowl. Add the eggs and vanilla extract and mix for about 2 minutes.

Step 4

Divide the batter between the two prepared pans and bake for 35 to 45 minutes, or until a toothpick inserted into the center of each cake comes out clean.

Step 5

Allow to cool for about 10 minutes in the pan, then turn the cakes out onto a wire cooling rack to cool completely.

Step 6

Add the butter to the bowl of a mixer and mix until smooth. Gradually add the powdered sugar, mixing well after each addition.

Step 7

Add the salt and cocoa powder. Mix well. Add the cooled chocolate and vanilla and mix well.

Step 8

Add the heavy cream to thin the buttercream to spreading consistency and mix to combine. Add more cream to make it thinner or more powdered sugar if you get it too thin.

Step 9

Once the cake is cool, trim off the domed part of each cake, and frost with the chocolate buttercream.