Prepare the pans and Oreos: Preheat your oven to 350°F (175°C). Spray two 9-inch round cake pans with floured baking spray. Place 15–19 Oreos flat in the bottom of each pan. This will give the cake layers a flavorful Oreo base, adding extra texture and sweetness as the cake bakes.
Make the cake batter: In a mixing bowl, blend the cocoa powder, sugar, cake flour, baking soda, and salt on low speed for 30 seconds. Add the eggs, Greek yogurt, and vanilla extract, mixing on medium speed for 1 minute until smooth. Stir in the hot coffee and finely chopped milk chocolate with a rubber spatula until fully combined. The coffee enhances the chocolate flavor, giving the cake a rich, deep taste.
Bake the cake layers: Divide the batter evenly between the two prepared pans, ensuring the Oreo layer remains intact. Tap the pans gently to remove any air bubbles. Bake for 28–32 minutes, or until a toothpick inserted into the center comes out clean. Allow the cakes to cool in the pans on a wire rack for 5–10 minutes, then remove from the pans and cool completely on wire racks.
Prepare the Oreo filling: In a medium bowl, cream together the butter and shortening until smooth. Gradually add the powdered sugar one cup at a time, alternating with milk and vanilla extract until thick and creamy. If the mixture is too thick, add a bit more milk until you reach your desired consistency.
Make the chocolate buttercream: In a mixing bowl, beat the butter and cocoa powder together on medium speed for 2 minutes until smooth and creamy. Gradually add the confectioners’ sugar, one cup at a time, alternating with milk until the frosting is smooth and spreadable. Beat for an additional 2 minutes until light and fluffy. Adjust the consistency by adding more sugar or milk if needed.
Assemble the cake: Place one cooled cake layer on a cake stand or serving platter with the Oreo side facing up. Spread the Oreo filling in an even 1-inch thick layer over the first cake layer. Add the second cake layer, with the Oreo side facing down. Press gently to secure the layers together.
Frost the cake: Cover the entire cake with the chocolate buttercream, smoothing it out with an offset spatula. Ensure that the top and sides are evenly coated with the frosting. The rich buttercream will create a perfect contrast to the soft, moist cake.
Decorate the cake: For decoration, crush the remaining Oreos or use a premade Oreo pie crust and scatter the crumbs along the edges and top of the cake. Press gently to ensure the crumbs stick to the frosting. This will give the cake a stunning, Oreo-covered look. Optionally, you can add extra Oreo pieces or chocolate chunks for more texture and flavor.
