Make room in your freezer for a 9" x 13" baking dish**. Set out your vanilla ice cream at room temperature.
Place the entire package of Oreos into a food processor and pulse until cookies form a fine crumb. Drizzle in the homemade magic shell until cookies are moist. Set aside.
Once your vanilla ice cream has sat out about 15 minutes, pour it into a large bowl and stir it with a large spatula to smooth it out. Once it is smooth and easily stirred, pour it into your baking dish. Spread the ice cream evenly into the bottom of the baking dish, making sure to fill in any holes and push ice cream into the very corners of your dish.
Sprinkle the cookie crumbs evenly over the vanilla layer, making sure to break up large cookie clusters with your fingers. Once you have used up all of the cookie crumbs, place baking sheet in the freezer to firm up, about 20 minutes. Set out your chocolate ice cream at this time.
Repeat step 4 with the chocolate ice cream, spreading the ice cream evenly over the cookie layer. Allow to set in the freezer, about 20 minutes.
While you wait for the cake to freeze, make your homemade whipped cream topping. Set aside until ready to use.
When your cake is firm, use a spatula to smooth the whipped cream topping over the chocolate ice cream layer. Decorate with sprinkles if desired. Allow to freeze completely in the freezer at least 12 hours, preferably 1 day. When you are ready to serve the cake, allow to sit at room temperature for about 5 minutes and use a very sharp knife to cut. Cover leftovers and store in the freezer up to 1 month.
*You can use any flavors of ice cream you wish in this recipe.**You will have the best results using a baking dish with a completely smooth bottom. I used one with ridges and the pieces on top of the ridges were very difficult to remove. Recipe inspired by Food Network