Prepare brownie mix as directed and bake in a 9 x 13 pan for 19-22 minutes or until edges appear done and center isn't quite set. Let cool completely and then freeze for 30 minutes.
Spread hot fudge topping on top of the brownies and top with chopped Oreos. Use an offset spatula to really press the cookies into the hot fudge topping. Smooth out the top and freeze for at least 30 minutes.
Spread ice cream over the hot fudge layer. Smooth out the top with an offset spatula. Cover with plastic wrap and freeze for at least six hours, preferably over night.
Top ice cream with caramel sauce. Smooth with an offset spatula.
Using a stand mixer or hand mixer, beat heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form.
Spread on top of caramel and smooth with an offset spatula. Freeze for at least 2 hours.
When ready to serve, top with Oreo cookie crumbs, additional whipped cream, and mini cookies.
Store in your freezer, tightly wrapped or in an airtight container for up to 3 weeks. Allow about 10 minutes at room temperature before cutting.