• Chocolate Cake Layers
• Preheat oven to 350°F / 175°C. Line 3, 8-inch round pans with parchment rounds and grease with non-stick baking spray or homemade pan release.
• Sift the flour, sugar, cocoa, baking powder, and salt into the bowl of a stand mixer or a large mixing bowl
• Mix chunks of room-temperature butter slowly into the dry mix, on a low speed using a paddle attachment or a hand mixer. Continue to mix until no chunks of butter remain and the mixture becomes crumbly. It should resemble moist sand.
• Pour in egg whites and mix on low until just incorporated.
• Mix in the buttermilk in two installments on a low speed.
• Scrape down the sides of the bowl with a spatula, then add in the vegetable oil, liquid espresso, and vanilla extract. Mix at a low speed until fully incorporated.
• Divide batter evenly between the prepared cake pans. I like to use a digital kitchen scale to weigh my pans. It helps make sure they all have the same amount of batter and this guarantees the layers will end up the same height.
• Bang the bottom of each pan on our counter. This helps removes any air bubbles before the pans are placed in the oven. I recommend placing a kitchen towel on the counter to make the process less loud.
• Bake for 32-34 minutes or until a toothpick inserted in the center of the cake comes out with a few moist crumbs. 
• Allow the layers to cool for 10 minutes on wire racks, then run an offset spatula around the perimeter of the pan to separate the cake from the pan.
• To accelerate the cooling process, I like to pop my cake layers in the freezer. You can also leave them on wire racks to finish cooling at room temperature.
• Once the layers are fully cooled, I like to level the top of each layer with a serrated knife.

Oreo Buttercream

• Beat the butter on a medium speed for 30 seconds with a paddle attachment, until smooth.
• Slowly add in the powdered sugar, 1 cup at a time. Place a kitchen towel over the stand mixer, to help reduce the powdered sugar clouds. Alternate with small splashes of cream.
• Once fully mixed, add in the vanilla extract and salt, and beat on low.
• Add in 1 cup of crushed Oreos (saving the rest for the cake decoration), and mix on low until the ingredients are fully incorporated, and the desired consistency is reached.
• If the frosting is too thick, add in additional cream (1 Tbsp at a time). If the frosting is too thin, add in more powdered sugar (1/4 cup at a time).
• Chocolate Drip
• Place 1/2 cup milk chocolate chips in a heat proof bowl and set aside.
• Heat 1/3 heavy cream in a heatproof bowl in the microwave for 45 seconds to 1 minute, until gently bubbling.
• If you don’t have a microwave or prefer to use the stove top, you can heat the cream over a medium heat in a pan until it begins to simmer. Remove from heat.
• Gently pour the heavy cream over the chocolate chips. Make sure they are covered with cream. Allow mixture to sit for 1-2 minutes.
• Stir until the cream and chocolate are fully combined and ganache is silky smooth.
• Let the mixture cool for about 20 minutes, until it is just slightly warm to the touch.
• Oreo Drip Cake Assembly
• Stack and frost cake layers on a greaseproof cake board using a dab of frosting to help secure the first cake layer to the board.
• Spread an even layer of Oreo buttercream between each cake layer with a large offset spatula and top with a large spoonful of crushed Oreos.
• Repeat with the remaining cake layers. Flip the top cake layer upside down to make it easier to frost.
• Spread a thin coat of frosting around the cake to fully cover the cake layers.
• Smooth using a bench scraper, then chill the cake in the fridge (30 minutes) or freezer (10 minutes) until the frosting is firm to the touch.
• Add a second, thicker layer of frosting to the cake and smooth using a bench scraper.
• Spoon crushed Oreos around the base of the cake, then use the offset spatula to carefully press them into the frosting.
• Chill the cake in the fridge (30 minutes) or freezer (10 minutes) again until the frosting is firm to the touch.
• While the cake chills, place the remaining frosting into a large piping bag fit with a Wilton 1M frosting tip (open star).
• Once the cake is chilled, add the chocolate ganache drips to the cake using a spoon or plastic squirt bottle.
• If you use a spoon, scoop up about a tsp of ganache and scrape the bottom of the spoon against the bowl. Add the ganache to the top of the cake (about ½ inch from the edge of the cake). Gently push the ganache over the edge of the cake with the spoon, and allow it to run down the side of the cake.
• Whether you use a spoon or squirt bottle, allow the first drip to be a test drip to check the consistency of the ganache.
• If the test drip seems too thick, try heating up the ganache for 5-10 additional seconds in the microwave. If the mixture seems too thin, allow it cool a bit longer, then try another test drip.
• Once the ganache is the right consistency, add drips around the entire cake. Pipe a ring of large buttercream swirls around the top of the cake using a Wilton 1M frosting tip and place an Oreo cookie vertically between each swirl.