Instructions:
Prepare three 8-inch cake pans with parchment paper circles in the bottom and grease the sides.
In a large bowl, whisk together all the dry ingredients for the chocolate cake.
Add eggs, milk, and vegetable oil to the dry ingredients and mix well.
Mix vanilla into boiling water and add it to the cake batter. Mix until well combined.
Divide the batter between the cake pans and bake at 300 degrees Fahrenheit for about 30-33 minutes, or until a toothpick comes out with a few crumbs.
Allow cakes to cool for about 10 minutes, then transfer them to cooling racks to cool completely.
While the cakes cool, prepare the Oreo buttercream by beating the softened butter until smooth. Gradually add 4 cups of powdered sugar and mix until smooth.
Add vanilla, Oreo crumbs, and salt and continue to mix until smooth.
Add another 4-5 cups of powdered sugar and mix until smooth, adjusting the consistency with water or milk if needed.
Reserve about 3 1/2 cups of icing for the filling inside the cake and add chopped Oreos, if using.
Once the cakes are cool, remove any domed tops with a serrated knife. Place the first cake layer on a cake plate and spread half of the Oreo icing with chopped Oreos on top in an even layer.
Add the second cake layer and spread the remaining Oreo icing with chopped Oreos on top in an even layer.
Add the final cake layer on top and frost the outside of the cake with the remaining frosting. You can use my tutorial for how to frost a smooth cake.
For the chocolate ganache, add the chocolate chips to a medium-sized bowl. Heat the heavy whipping cream until it begins to boil, then pour it over the chocolate chips. Let it sit for 2-3 minutes, then whisk until smooth.
Drizzle the chocolate ganache around the edge of the cake, then pour the remainder on top and spread it evenly.
Allow the ganache to firm up slightly, then pipe the remaining frosting around the top edge of the cake and place an Oreo between each swirl (using Ateco tip 844).
Sprinkle a few Oreo crumbs onto the cake, if desired, then serve. The cake is best when well covered for 3-4 days.
