Make the Cake Layers

1. Prepare three 8 inch cake pans with parchment paper circles in the bottom and grease the sides. Preheat oven to 350°F (176°C).
2. Combine the flour, baking powder and salt in a medium sized bowl and set aside.
3. Add the butter, vegetable oil and sugar to a large mixer bowl and beat together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
4. Add the eggs one at a time, mixing until well combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
5. Add half of the dry ingredients to the batter and mix until combined.
6. Add the buttermilk and vanilla extract and mix until well combined.
7. Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
8. Fold the chopped Oreos into the batter.
9. Divide the batter evenly between the cakes pans and bake for 18-23 minutes, or until a toothpick comes out with a few crumbs.
10. Remove the cakes from the oven and allow to cool for about 2-3 minutes, then remove to cooling racks to cool completely.

Make the Buttercream

1. Beat the butter until smooth.
2. Slowly add half of the powdered sugar and mix until smooth.
3. Add the vanilla extract, 4-5 tablespoons of water or cream and salt and mix until smooth.
4. Slowly add the remaining powdered sugar and mix until smooth. Add additional water or cream, as needed to get the right consistency of frosting.

Assemble the Cake

1. Use a large serrated knife to remove the domes from the top of the cakes so that they’re flat. These cakes don’t have a large dome, but I like to make sure they’re completely flat.
2. Place the first cake on a serving plate or a cardboard cake round.
3. Spread about 1 cup of frosting evenly on top of the cake, then sprinkle with about 1/2 cup of chopped Oreos. Press the Oreos down into the frosting.
4. Add the second layer of cake and another cup of frosting and another 1/2 cup of chopped Oreos.
5. Top the cake with the remaining layer and frost the outside of the cake. Refer to my tutorial for frosting a smooth cake, if needed.
6. Press chopped Oreos into the sides of the cake immediately after frosting it. If you wait, the buttercream will “crust” and things won’t stick as well.
7. Pipe swirls of frosting around the top edge of the cake, adding half an Oreo between each swirl. I used Ateco tip 847.