Preheat your oven to 350°F (175°C). Grease two 9-inches round cake pans and line the bottoms with parchment paper for easy release.
In a large bowl, combine Devil’s Food cake mix, chocolate pudding mix, eggs, vanilla, oil, sour cream (or buttermilk), and cooled coffee. Beat with an electric mixer on medium speed for about 2 minutes, until the batter is smooth and thick.
Fold in chocolate chips by hand with a spatula until evenly distributed.
Divide the batter between the pans and bake for 45–50 minutes, or until a toothpick comes out with a few moist crumbs. Let the cakes cool in the pans for 10 minutes, and then turn out onto wire racks to cool completely.
For the frosting, beat very soft butter until creamy. Gradually mix in sifted cocoa powder and powdered sugar. Add vanilla, a pinch of salt, heavy cream, and hot fudge sauce. Beat on high until fluffy. Add more cream if needed for a spreadable consistency.
To assemble, level the cake layers if needed. Frost the first layer, add the second, then cover the top and sides. Decorate with ganache, chocolate chips, or shavings if desired. Enjoy! This cake is rich, moist, and loaded with chocolate goodness.