Take your chocolate ice cream out of the freezer and let it soften for 10 to 20 minutes (Note 3). Proceed to the next step of preparing your springform pan in the meantime.
Line the bottom and insides of a 9-inch springform pan with plastic wrap.
Transfer the chocolate ice cream to the springform pan and use a spatula to spread it out into an even layer. Place the pan in the freezer for 30 minutes.
Place the crushed cookies into a medium bowl, and add the melted butter. Stir to combine the cookie crumbs and butter.
If the hot fudge has been in the fridge, warm it up slightly, just so that it's spreadable but not hot enough to melt the ice cream.
Take the pan out of the freezer. Spread the fudge in an even layer over the chocolate ice cream, then top the fudge with the cookie crumbs. Press the crumbs into the fudge. Return the pan to the freezer for 30 minutes.
Take the vanilla ice cream out of the freezer to soften 10 to 20 minutes before you're ready to remove the cake pan from the freezer.
Spread the vanilla ice cream over the cookie layer, using a spatula and/or bench scraper to smooth and level it out.
Return the pan to the freezer for at least 2 hours, until the ice cream feels solid.
To make the frosting, place the coconut cream into a large mixing bowl. Use an electric mixer at high speed to beat it until creamy, about one minute. Add the powdered sugar, a bit at a time, then the vanilla. Place the bowl in the fridge to chill while you get the cake ready to be frosted.
Remove the cake from the freezer, then carefully release the springform pan. Invert the cake onto a plate, remove the base of the springform pan and peel off the plastic.
Take the frosting out of the fridge, then spread the frosting over the top and sides of the cake.
Optionally, decorate the cake with sprinkles and whipped cream.
Place the cake into the freezer and freeze it until the frosting and toppings are set.
Slice and serve.