Line two 9-inch round cake pans with parchment paper and spray lightly with a non-stick baking spray.
In a large bowl , combine flour, sugar, cocoa, baking soda, baking powder and salt.
Add in the eggs, sour cream, vanilla and oil, mixing well with an electric mixer. Stir in the coffee.
Pour cake batter into the pans and bake on the center rack of your oven for about 30 minutes until a toothpick inserted into the center of the cake comes out clean.
Remove cake from oven and cool completely on wire racks.
After completely cool, you can remove the top dome off of one of the cakes so they will stack well. You can use a large knife for this or a cake leveler.
Filling
In a large bowl and using an electric mixer, whip up the solid shortening softened butter, granulated sugar, evaporated milk and vanilla for about 10 minutes. Mixture will be light and fluffy.
Place the cake layer that you have trimmed the dome onto a serving platter with the cut side up.
Spread the filling heavily onto the bottom layer, covering well to the edges. Try to smooth the icing evenly across the cake.
Place the top layer on top of the filling.
Chocolate Icing
Combine melted butter and cocoa powder. Add the powdered sugar, vanilla and buttermilk. Mix on high speed until smooth and creamy. If icing seems too thick to spread easily, add a little milk, a tablespoon at a time until the desired consistency.
Spread icing evenly across the top and sides of the cake.
Refrigerate the cake for several hours before serving.
Notes
If you don't have buttermilk on hand, you can add 1 tablespoon of white vinegar to a cup of milk as a substitute.
A cake leveler is a handy tool to remove the dome of the cake to allow the layers to stack well.
An offset spatula is very helpful to spread the icing onto the sides of the cake.
This recipe can also be baked in a 13x9 inch pan if you like. You can either put the filling on the top of the cake and then ice on that or you can cut the cake into layers and fill between the layers.