Preheat the oven to 350F degrees.
Lightly grease the sides of a 9 inch springform pan and line the bottom with parchment paper.
Prepare the brownie mix according to package instructions, then bake (it'll take a few minutes less than the time for a 9x9 inch square pan).
Allow the brownies to cool, and take the ice cream out of the freezer to soften.
Spoon the ice cream over the cooled brownie and spread the top flat.
Place in the freezer to harden for 1 hour.
Whip the heavy cream until stiff peaks form, then spread a layer over top of the ice cream and decorate with rosettes (optional).
Sprinkle with crushed Oreo cookies.
Place the cake back in the freezer for 3 hours or until read to serve.
*Store the cake in the freezer.