Devil's Food Cake: Preheat your oven to 350 degrees F (180 degrees C) and place your oven rack in the center of the oven. Butter, or spray with a non stick vegetable spray, two - 8 inch (20 cm) cake pans. Then line the bottoms of the pans with parchment paper. 

In a separate bowl, whisk the cocoa with the hot coffee (or water) until the cocoa has dissolved and the mixture is nice and smooth. This whisk in the sour cream (or plain yogurt) and vanilla extract.

In a large bowl whisk or sift together the flour, baking soda, and salt.

Then, in the bowl of your electric stand mixer, fitted with the paddle attachment (or with a hand mixer), beat the butter until smooth. Add the sugar and oil and beat, on medium high speed, until the mixture is soft and fluffy, and light in color (this will take about 3-4 minutes). Add the eggs, one at a time, mixing well after each addition. Scrape down the sides and bottom of the bowl as needed.

Add the flour mixture (in three additions) alternately with the cocoa/sour cream mixture (in two additions), beginning and ending with the flour mixture. Beat only until the ingredients are incorporated.

Divide the batter evenly between the two prepared pans (about 580 grams each) and smooth the tops with an offset spatula or the back of a spoon. Bake for about 30-35 minutes or until a toothpick inserted in the center comes out clean and the tops spring back when lightly pressed. Remove from oven and place on a wire rack to cool (in their pans) for about 10 minutes. Then, one cake at a time, place a wire rack on top of the cake pan and invert, lifting off the pan. Remove the parchment paper and then, to prevent cracks, reinvert the cake onto a greased wire rack so that tops are right side up. Cool completely before frosting.

Chocolate Frosting: Melt the chocolate in a heatproof bowl placed over a saucepan of simmering water. Remove from heat and let cool to room temperature.

In the bowl of your electric stand mixer, fitted with the paddle attachment (or with a hand mixer), beat the butter until smooth and creamy (about 1 minute). Add the sugar and beat until it is light and fluffy (about 2 minutes). Beat in the vanilla extract. Add the chocolate and beat on low speed until incorporated. Increase the speed to medium-high and beat until frosting is smooth and glossy (about 2 - 3 minutes).

Assemble: Place one cake layer on your serving plate and spread with about 1 cup (240 ml) of frosting. Place the other cake layer on top of the frosting and cover the entire cake with the remaining frosting.

Serves about 10 - 12 people.