Make the whipped cream right before you plan on topping the ice cream cake (it will keep in the freezer for up to 2 months after adding it). Get started by chilling the metal bowl of your stand mixer in the refrigerator or freezer for 10-15 minutes.
Sprinkle the gelatin into a small glass measuring cup or microwave safe dish. Add the cold water and whisk until the gelatin is dissolved. Set the mixture aside for 5 minutes to let the gelatin set.
While the gelatin is setting, add the heavy whipping cream, powdered sugar, and vanilla extract into the chilled metal bowl of your stand mixer fitted with the paddle attachment and mix on low speed to combine. Turn the mixer to high speed and beat until the mixture is thickened, stopping just shy of reaching soft peaks, about 1 min.
At this point, the gelatin should be solidified. If so, pop it into the microwave for 5-10 seconds, until the mixture has re-liquified but is still cool to the touch. Use a whisk to briefly stir the gelatin mixture together to make sure it's smooth.
With the mixer on low speed, drizzle the liquid gelatin into the cream. Slowly increase the speed to medium-high and continue to beat until you have reached stiff, fluffy peaks, about 2 minutes.
Remove the ice cream cake from the freezer and add all of the whipped cream frosting on top. Smooth it down with an angled spatula and frost some swoops and swirls into the surface to make the texture rustic. While the whipped cream frosting is still tacky, top it with crushed and/or chopped Oreos. Place back in the freezer until you’re ready to serve (covered with aluminum foil or plastic wrap). When you’re ready to serve the cake, remove the collar of the springform pan and slice! If you want to display the cake before serving, you can take it out of the freezer about 20-30 minutes before serving. Longer than that and it will begin to soften (but will still taste amazing).