1. Preheat oven to 350 degrees F. Grease and line 3 8-inch round cake pans with parchment paper. Dust bottom and sides with cocoa powder.
2. In a medium bowl, whisk to combine the cocoa powder and espresso/coffee powder. Add the boiling water and whisk until smooth. Set aside to cool slightly (2-3 minutes). Once cooled off, add the sour cream and vanilla and whisk to combine. Set aside.
3. In another medium bowl, combine the flour, baking soda, and salt, and whisk to combine. Set aside.
4. In the bowl of an electric mixer (I use my paddle attachment), beat the butter and sugar on medium-high speed until light and fluffy (3-4 minutes).
5. Add the eggs one at a time and beat to combine.
6. With your mixer on low speed and starting and ending with the flour mixture, alternatively add the flour mixture and the chocolate mixture to the butter and sugar, beating each addition on low speed until just combined.
7. Divide the batter evenly between the prepared pans and bake for 30 to 32 minutes, or until a toothpick in the center comes out clean. Let cool in the pans for 30 minutes, then remove and transfer to a wire rack to cool completely.
8. To make the frosting, use your electric mixer fitted with the paddle attachment and beat butter and shortening together until smooth (1 minute). Slowly add the powdered sugar and beat until just combined. Add vanilla extract and 3 tablespoons of hot water. Beat on medium-low speed for 5-10 minutes, or until light and fluffy. Add more water or powdered sugar as needed to get the perfect consistency. Add crushed Oreos and beat on low speed until smooth.
9. To make the chocolate ganache, add chocolate to a medium sized bowl. In another bowl, heat heavy cream in the microwave for 40-60 seconds. Pour the heavy cream over the chocolate and let sit for about 5 minutes. Stir until smooth and let cool completely before using on the cake.

To Assemble:

1. Place one cake layer upside down on a cake plate or stand and spread about 1-2 cups of frosting on cake. Repeat with second layer. Add third cake layer and frost a thin layer on sides and top. This is your crumb coat, and I usually stick it in the fridge or freezer for 15 minutes at this point.
2. Reserve about 1/2 cup of frosting in a pastry bag fitted with a decorative tip (I used #1M).
3. Once the crumb coat is set, add additional frosting to the top and sides of the cake. Use an offset spatula for a smooth finish.
4. Add the cooled chocolate ganache to a squeeze bottle and drip along the edges of the cake.
5. Use the reserved frosting in pastry bag to pipe swirls or any decorations along the top border of the cake.
6. Finish by garnishing with Oreo fourths on top of swirls. (Tip: To easily cut Oreos, place them in the freezer for 5-10 minutes before cutting).