1. Remove ingredients that need to be at room temperature from the fridge: butter, eggs, sour cream and milk. Let that sit on the counter for 1 hour.
2. Preheat oven to 350°F. Grease and line three 8 inch cake pans with parchment paper.
3. In a medium bowl, combine the flour, cocoa powder, baking powder and salt. Whisk until combined well.
4. In the bowl of your stand mixer with the whisk attachment, beat the butter and sugar on medium-high speed for 2 minutes. Add the oil and beat for another 2 minutes on medium-high speed.
5. Add the eggs, one at a time, beating for 30 seconds on medium speed, until incorporated.
6. Add the vanilla, espresso powder and sour cream. Mix on low until just combined, about 30 seconds.
7. With the mixer off, add half of the flour mixture. Then turn the mixer on low speed. Stream in the milk. Turn off the mixer and add the remaining half of the flour. Turn the mixer back on to low speed and mix for another 30 seconds, until just a small amount of streaks remain. Remove the bowl from the mixer stand and use a silicone spatula to scrape the bottom and sides of the bowl to complete the mix by hand.
8. Pour the batter into the three prepared cake pans, distributing evenly, about 19 ounces in each pan.
9. Bake for 32 to 35 minutes. Use a cake tester or gently press down on the the center of the cake. If it springs back, it is done.
10. Remove the cakes from the pans and place on a cooling rack. Let it come to room temperature before frosting or refrigerate until ready to frost.

Chocolate Ganache

1. In a small saucepan, heat the cream until it starts to simmer and bubble around the edge of the pan.
2. Place the chocolate in a medium bowl and pour the hot cream over the chocolate. Cover and let that sit for 5 minutes.
3. With a silicone spatula, stir the mixture until it becomes smooth. This is the ganache. Cover the bowl again and let the ganache come to room temperature.
4. Pour half of the ganache into the bowl of your stand mixer. With the whisk attachment on medium high speed, whisk for 5 minutes until the ganache is fluffy and lighter in color. Now you have both whipped ganache and regular (un-whipped) ganache. Time to assemble!

Assemble

1. Place the first layer of cake on a board or the plate of a cake holder. Using a piping bag with the whipped ganache, pipe a border around the edge of the cake. Place this piped cake in the fridge for 15 to 30 minutes for the piped whipped ganache boarder to firm up a little bit.
2. Remove the cake from the fridge. Using half of the reserved regular un-whipped ganache, fill the center of the cake inside the piped boarder. Place the second layer of cake on top. Pipe a border around the edge of the cake with the whipped ganache. Refrigerate in the fridge for 15 to 30 minutes, for the newly piped border to firm up. This will also help keep the bottom layer firmly in place and prevent sliding.
3. Remove the cake from the fridge and fill the center of the second cake layer with the remaining regular ganache inside the piped border. Top with the last layer of cake. Use the rest of the whipped ganache to frost the outside of the cake. You should have enough to lightly frost this 3 layer cake all around. Refrigerate the cake.

Chocolate Drip

1. Place the chocolate in a medium bowl. In a small saucepan, heat up the cream until it starts to simmer and bubble around the edges of the pan. Pour the cream into the bowl with the chocolate. Cover and let that sit for 5 minutes.
2. With a silicone spatula, gently stir the mixture until completely smooth. Cover and let that cool for 10 minutes.
3. Add about 2 ounces of room temperature ganache in to a squeeze bottle. Hold the tip of the squeeze bottle on the top edge of the cake. Start squeezing the chocolate along the edge. While squeezing the bottle, pause whenever you want a drip to fall off the edge of the cake, then continue along the edge, pausing every time you want a drip to fall. Go all around the perimeter of the cake.
4. Pour the remaining ganache over the top of the cake. Spread to it form an even layer.
5. Refrigerate the cake to let it set. This cake is best served 30 minutes after removing from the fridge. Or an hour. Or immediately. All good.