Start by preparing three 8-inch cake pans with parchment paper circles at the bottom and greasing the sides. In a large bowl, whisk together all the dry ingredients. Add the eggs, milk, and vegetable oil to the dry mixture and mix thoroughly. Stir in the vanilla extract with the boiling water, then combine it with the rest of the mixture. Divide the batter evenly between the three cake pans. Bake at 300°F for 30-33 minutes, or until a toothpick inserted into the center comes out with a few crumbs. Once done, remove the cakes from the oven and let them cool for about 10 minutes. Afterward, transfer the cakes to cooling racks to cool completely.

While the cakes are cooling, begin preparing the icing. Beat the butter in a mixing bowl until smooth. Gradually add 4 cups of powdered sugar and mix until fully incorporated. Then add the vanilla extract, Oreo crumbs, and a pinch of salt, mixing until smooth. Slowly add the remaining 4-5 cups of powdered sugar, mixing after each addition. If the frosting is too thick, add heavy cream as needed until you achieve a smooth consistency.

To prepare the filling, measure out about 3½ cups of the Oreo buttercream and stir in the chopped Oreos. Set this filling aside. Keep the remaining Oreo buttercream for frosting the outside of the cake.

Once the cakes are fully cooled, use a large serrated knife to remove the domed tops. Place the first cake layer on a cake plate. Spread half of the chopped Oreo filling evenly over the top. Add the second cake layer and spread the remaining chopped Oreo filling on top in an even layer. Place the final cake layer on top and frost the outside of the cake with the Oreo buttercream frosting. For a smooth finish, refer to my frosting tutorial.

To make the ganache, place the chocolate chips in a medium-sized bowl. Heat the heavy whipping cream just until it begins to boil, then pour it over the chocolate chips. Let the mixture sit for 2-3 minutes, then whisk until smooth. Drizzle the ganache around the edges of the cake, then pour the remaining ganache on top and spread it evenly. I prefer to use a squeeze bottle for the drizzling around the edges.

Finish the Cake:

Allow the ganache to firm up slightly. Once it has set, pipe the remaining Oreo buttercream frosting around the top edge of the cake (for piping, I used Ateco tip 844) and add an Oreo between each swirl. If desired, sprinkle some Oreo crumbs over the top of the cake for extra texture and decoration. Let the cake set before serving.