Preheat the oven to 350 degrees and spray 3- 6″ round pans with baking spray. Ideally baking spray with flour.
In a bowl combine the cake mix, pudding mix, butter, milk, and eggs. Stir in the crushed oreos.
Divide the batter evenly among the 3 round pans and bake according to the package directions. Let the cakes cool in the pan for several minutes, then move to wire racks to cool completely.
Meanwhile, beat 3 sticks of butter until smooth. Add in half of the powdered sugar and mix. Add the rest of the sugar, vanilla, and heavy cream. Once fully mixed, add in the cookies and mix until incorporated.
Once the cake is cool, place one round on a cake board. Top with a layer of frosting making sure to frost all the way to the edges. Repeat and end with the final round on top.
Using the offset spatula, spread an even layer of frosting around the entire cake. This will be the crumb coat. Place in the fridge for 10-15 minutes to set.
While in the fridge, make the ganache. Heat heavy cream for one min in the microwave. Add in chocolate chips and let it sit for 30 seconds, then stir with a whisk. It’ll take a couple of minutes to come together. Let it cool then transfer it to a squeeze bottle if desired.
Remove the cake from the fridge and apply a second layer of frosting. Using your hand, press a layer of sprinkles along the bottom. *Tip- if you put a rimmed baking sheet under the cake it’ll catch any fallen sprinkles.
Place back in the fridge for 5 minutes
Remove the cake from the fridge again and apply the ganache drip. Using your squeeze bottle, make drips along the edge of the cake and finish with extra ganache in the center. Alternately, you can use a spoon and press the ganache over the edge. Return to the fridge.
Once the ganache is set, using a large piping tip, add swirls around the top border of the cake. Top with mini sandwich cookies, peppermints, and extra sprinkles