Make the Brownie Base:
Grease an 8×3 inch springform cake pan and line the bottom with parchment paper for easy removal.
Prepare the brownie batter according to the instructions on the box and bake in the prepared pan.
Allow the brownie to cool completely. Once cool, remove the brownie base from the pan.
Note: Wash and dry the springform pan for use later when assembling the cake.
Make the Ice Cream Layers:
In a large mixer bowl, combine the softened cream cheese, sugar, and brown sugar. Mix until smooth.
Add the milk and vanilla extract, mixing until smooth. Set aside.
In another mixer bowl, whip the cold heavy whipping cream and powdered sugar on high speed until stiff peaks form.
Gently fold about 1/3 of the whipped cream into the cream cheese mixture until combined, then fold in the remaining whipped cream.
Divide the ice cream mixture evenly between two bowls.
In one bowl, add the chocolate chip cookie crumbs, chopped chocolate chip cookies, and mini chocolate chips. Fold to combine. Set aside.
In the other bowl, add the Oreo crumbs and chopped Oreos. Fold to combine. Set aside.
Make the First Batch of Ganache:
Add 3 oz of chocolate chips to a small bowl.
Heat 1/4 cup of heavy whipping cream in a microwave-safe bowl until it begins to boil. Pour the hot cream over the chocolate chips and let it sit undisturbed for 3-4 minutes. Whisk until smooth. Set aside.
Build the Cake:
Line the sides of your cleaned and dried 8-inch springform pan with parchment paper. Ensure the parchment sticks up above the top edge of the pan.
Place the cooled brownie base back into the prepared pan.
Add the chocolate chip cookie ice cream on top of the brownie, spreading it into an even layer.
Cover with a layer of chocolate ganache and spread into an even layer.
Add the Oreo ice cream on top of the ganache and spread into an even layer.
Freeze the cake for 6-8 hours or overnight until fully frozen.
Finish the Cake:
Once the cake is fully set, prepare the toppings.
Chop or crumble brownies, Oreos, and chocolate chip cookies. Set aside.
Make the second, larger batch of chocolate ganache by placing the remaining 6 oz of chocolate chips in a small bowl.
Heat the remaining 1/2 cup of heavy whipping cream in a microwave-safe bowl until it begins to boil. Pour it over the chocolate chips and let it sit undisturbed for 3-4 minutes, then whisk until smooth. Set aside.
Make the chocolate whipped cream by adding the cold heavy whipping cream, powdered sugar, and cocoa powder to a large mixer bowl. Whip on high speed until stiff peaks form.
Place the chocolate whipped cream into a piping bag and set aside.
Remove the frozen cake from the pan and peel away the parchment paper.
Drizzle the ganache around the edge of the cake, using a squeeze bottle or spoon.
Fill the center of the cake with ganache, smoothing it into an even layer.
Pipe a small dome of chocolate whipped cream onto the center of the cake. Top with brownie chunks, Oreos, chocolate chip cookies, and mini chocolate chips.
Freeze the cake until ready to serve. Let the cake soften for about 30 minutes at room temperature before cutting slices. Serve promptly and return leftovers to the freezer. Best eaten within 4-6 days.