Preparation Steps

• Preheat oven to 350°F. Prepare three 8-inch cake pans by greasing sides and lining bottoms with parchment paper.
• In a medium bowl, mix together the flour, baking powder, and salt. Set aside.
• In a large bowl, beat the butter, vegetable oil, and sugar until light and fluffy, about 3-4 minutes.
• Add eggs one at a time mixing well after each addition, scraping down sides as needed.
• Add half the dry ingredient mixture and mix until just combined.
• Mix in the buttermilk and vanilla extract until fully combined.
• Add the remaining dry ingredients and mix until smooth, being careful not to overmix.
• Fold chopped Oreos into the batter gently.
• Divide the batter evenly into the prepared pans and bake for 18-23 minutes or until a toothpick inserted comes out with a few crumbs.
• Allow cakes to cool 2-3 minutes in pans then transfer to wire racks to cool completely.
• For the buttercream: beat butter until smooth. Gradually add half the powdered sugar and beat until smooth.
• Add vanilla extract, 4-5 tablespoons water or cream, and salt; mix until smooth.
• Slowly add remaining powdered sugar, mixing until creamy. Add more water or cream if needed for desired consistency.
• Level cake tops with a serrated knife to create flat layers.
• Place first cake layer on a serving plate or cake board.
• Spread about 1 cup of frosting over the first layer and sprinkle with 1/2 cup chopped Oreos, gently pressing them into the frosting.
• Add the second cake layer and repeat with another cup of frosting and 1/2 cup Oreos.
• Top with final cake layer and frost the outside of the entire cake smoothly.
• Press chopped Oreos into the sides of the cake before the frosting crusts over.
• Pipe swirls of frosting around the top edge of the cake, placing half an Oreo between each swirl for decoration.